Radio communication system, method, device and computer readable medium including first and second receiving signals respectively allocated to first and second overlapping subcarriers

ABSTRACT

A communication device comprising at least a receiver and a demodulator. The receiver receives first receiving signals and second receiving signals, wherein the first receiving signals are allocated to a first set of subcarriers composed of two or more continuous subcarriers, the second receiving signals are allocated to a second set of subcarriers composed of two or more continuous subcarriers, and at least a portion of the second set of subcarriers overlaps a portion of the first set of subcarriers in a time frame. The demodulator configured to detect the second receiving signals transmitted using one or more subcarriers from receiving signals including the first receiving signals and the second receiving signals, wherein the one or more subcarriers are subcarriers such that the first set of subcarriers overlap the second set of subcarriers, and the demodulator being demodulates the first receiving signals.

This application is a Continuation of co-pending application Ser. No.14/199,538 filed on Mar. 6, 2014, which is a Divisional of applicationSer. No. 12/673,340 filed on Feb. 12, 2010, now U.S. Pat. No. 8,699,319B2 issued Apr. 15, 2015, and for which priority is claimed under 35U.S.C. §120, application Ser. No. 12/673,340 is the national phase ofPCT International Application No. PCT/JP2008/064545 filed on Aug. 13,2008 under 35 U.S.C. §371, which claims the benefit of priority ofJP2007-210936 filed Aug. 13, 2007, and JP2007-210937 filed Aug. 13,2007. The entire contents of each of the above-identified applicationsare hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a radio communication system, a radiocommunication method, a radio communication device, a reception device,and a program.

BACKGROUND ART

Recently, next-generation mobile communication systems have beenactively studied. As a method for enhancing the frequency utilizationefficiency of a system, a single-frequency reuse cellular system hasbeen proposed in which each cell uses the same frequency band so thateach cell can use the entire band allocated to the system.

OFDMA (Orthogonal Frequency Division Multiple Access) is a front-runnerin a downlink (communication from a base station device to a mobilestation device). OFDMA is a communication system in which informationdata are modulated by use of different modulation schemes, such as 64QAM (64-ary Quadrature Amplitude Modulation) and BPSK (Binary PhaseShift Keying), according to reception conditions to generate an OFDMsignal, and radio resources defined by time-and-frequency axes areflexibly allocated to multiple mobile station devices.

Since an OFDM signal is used in this case, a PAPR (Peak to Average PowerRatio) becomes greatly high in some cases. The high peak power is not asevere problem for downlink communication having a relatively-hightransmission-power amplifying function. However, the high peak power isa fatal problem for uplink communication (from the mobile station deviceto the base station device) having a relatively-low transmission-poweramplifying function.

For this reason, a single-carrier-based communication scheme with a lowPAPR is suitable to the uplink (communication from the mobile stationdevice to the base station device).

However, the use of the single-carrier scheme causes a problem thatflexible resource allocation using time-and-frequency axes cannot beperformed such as in the case of OFDM. To solve the problem, SC-ASA(Single Carrier-Adaptive Spectrum Allocation), which is also calledDFT-S-OFDM (Discrete Fourier Transform-Spread OFDM), has been proposed(see, for example, Non-Patent Document 1).

Such a communication scheme uses the same scheme as the single-carriercommunication scheme, resulting in a lower PAPR. Additionally, a cyclicprefix is inserted as in the case of OFDM signals, enabling dataprocessing without inter-block interference (in this description, aninterval at which a cyclic prefix is inserted, i.e., data processingunit by which DFT is performed, is called a DFT-S-OFDM symbol). Further,frequency waves are generated once by use of DFT, thereby simplifyingresource control per subcarrier.

FIG. 40 illustrates a configuration of a transmission device when MIMO(Multi-Input Multi-Output) transmission using SC-ASA is performed. FIG.40 may be regarded as illustrating one transmission device includingmultiple transmission systems or as illustrating different transmissiondevices. This respect is explained hereinafter. In FIG. 41A, one basestation wirelessly communicates with two mobile stations. Each of thebase station and the mobile stations includes two antennas. If theconfiguration of the transmission device shown in FIG. 40 is regarded asone transmission device including multiple transmission systems, FIG. 40is regarded as illustrating a case of single-user MIMO shown in FIG.41C. If the configuration of the transmission device is regarded asdifferent transmission devices, FIG. 40 is regarded as illustrating acase of multi-user MIMO shown in FIG. 41B. Subcarriers to be used aredenoted as white blocks. Subcarriers corresponding to the numbers, whichare not denoted as white blocks, are ones not selected in SC-ASA.

Regarding each transmission system shown in FIG. 40, transmission data 1and 2 are encoded by encoders 1000 and 1001, and then modulated bymodulators 1002 and 1003, respectively. The modulated signals areconverted into parallel signals by S/P (Serial/Parallel) converters 1004and 1005, and then converted into frequency-domain signals by DFT units1006 and 1007, respectively. Spectral mapping units 1008 and 1009perform mapping such that the transmission data 1 and 2 use the samefrequency subcarriers as shown in FIGS. 41B and 41C. Subcarriers havinghigh received SNR or SINR are used in the case of SC-ASA. However, MIMOtransmission causes signals transmitted from the two transmissionsystems to interfere with each other on the receiving side. For thisreason, common subcarriers having good conditions have to be selectedfor the transmission antennas (users) in consideration of the degree ofthe interference and all channels among the two transmission systems andthe two reception systems.

Then, the mapped frequency-domain signals are converted into time-domainsignals by IDFT units 1010 and 1011, and then converted into serialsignals by P/S (parallel/signal) converters 1012 and 1013. Then, cyclicprefixes are inserted by CP inserters 1014 and 1015, and then convertedinto analog signals by D/A converters 1016 and 1017. Finally, the analogsignals are upconverted into radio-frequency signals by radio units 1018and 1019, and then transmitted from the transmission antennas 1020 and1021.

FIG. 42 is a schematic block diagram illustrating a configuration of areception device receiving signals transmitted by the MIMO systems.Since the reception device shown in FIG. 42 includes a canceller, thereception device having such a configuration can achieve betterreception characteristics. The device shown in FIG. 42 includes:antennas 1100 and 1101; RF units 1102 and 1103; A/D converters 1104 and1105; CP removers 1106 and 1107; S/P converters 1108, 1109, 1133, and1134; DFT units 1110, 1111, 1116, 1117, 1135, and 1136; channelestimators 1112 and 1113; a canceller 1114; a signalequalizing-and-demultiplexing unit 1115; a spectral demapping unit 1118;IDFT units 1119, 1120, 1138, and 1139; P/S converters 1121 and 1122;demodulators 1123 and 1124; decoders 1125 and 1126; repetitioncontrollers 1127 and 1128; determining units 1129 and 1130; replicagenerators 1131 and 1132; a spectral mapping unit 1137; and a channelmultiplier 1140.

The signals transmitted from the transmission device shown in FIG. 40are received by the antennas 1100 and 1101 of the reception device,downconverted from radio-frequency signals by the RF units 1102 and1103, and then converted into digital signals by the A/D converters 1104and 1105. Then, the cyclic prefixes CP (GI) added on the transmittingside are removed by the CP removers 1106 and 1107. Then, the signalswith the cyclic prefixes removed are converted into parallel signals bythe S/P converters 1108 and 1109, and then converted intofrequency-domain signals by being subjected to DFT performed by the DFTunits 1110 and 1111. Channel estimation between each transmissionantenna and each reception antenna is performed using a known signaladded on the transmitting side as a signal for channel estimation, theknown signal being included in the converted frequency-domain signal. Inthis case, channel estimation values for the number of subcarriers arecalculated with respect to 4 channels=the number of transmissionantennas×the number of reception antennas.

The data signals subjected to DFT and then converted into thefrequency-domain signals are input to the canceller 1114. The canceller1114 subtracts, from the received signals, replicas of received signals,which are generated based on the reliability of demodulated data. If aperfect replica (transmitted signal) is generated, an output of thecanceller 1114 includes only noise elements. This calculation can beexpressed as an expression (100) where R denotes a reception-data vectorreceived by the two antennas, Ξ denotes a channel matrix, and S′ denotesa replica of a transmission-data vector (generated by a replicagenerator to a spectral mapping unit as will be explained later).Q=R−ΞS′  (100)

Q denotes a vector indicating an output of the canceller 1114 at thetime of second-or-more repeated operation (i.e., a residual aftercancelling). R, Ξ, S′ are shown in the following expressions (101) to(103), where a figure in a parenthesis denotes the subcarrier number,and an index denotes the transmission-and-reception antenna number. Twoindexes of Ξ denote a combination of reception-and-transmissionantennas. For example, Ξ₂₁ denotes a channel from the transmissionantenna 1 to the reception antenna 2. These expressions may be used forboth single-user MIMO and multi-user MIMO.

$\begin{matrix}{\mspace{79mu}{R = \begin{bmatrix}{\;{R_{\; 1}\;(1)}} \\{\;{R_{\; 1}\;(2)}} \\{\;{R_{\; 1}\;(3)}} \\{\;{R_{\; 1}\;(4)}} \\{\;{R_{\; 2}\;(1)}} \\{\;{R_{\; 2}\;(2)}} \\{\;{R_{\; 2}\;(3)}} \\{\;{R_{\; 2}\;(4)}}\end{bmatrix}}} & (101) \\{\Xi = {\quad\begin{bmatrix}{\;{\Xi_{\; 11}\;(1)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 12}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 11}\;(2)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 12}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 11}\;(4)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 12}\;(4)}} \\{\;{\Xi_{\; 21}\;(1)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 22}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 21}\;(2)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 22}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 21}\;(4)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 22}\;(4)}}\end{bmatrix}}} & (102) \\{\mspace{79mu}{S^{\prime} = \begin{bmatrix}{\;{S_{\; 1}^{\;\prime}\;(1)}} \\{\;{S_{\; 1}^{\;\prime}\;(2)}} \\0 \\{\;{S_{\; 1}^{\;\prime}\;(4)}} \\{\;{S_{\; 2}^{\;\prime}\;(1)}} \\{\;{S_{\; 2}^{\;\prime}\;(2)}} \\0 \\{\;{S_{\; 2}^{\;\prime}\;(4)}}\end{bmatrix}}} & (103)\end{matrix}$

The reason that replicas (ΞS′) of all signals including desired signalsto be extracted are cancelled is that the signalequalizing-and-demultiplexing unit 1115 that will be explained laterperforms an inverse matrix calculation, and therefore the inverse matrixcalculation has to be performed a number of times corresponding to thenumber of desired signals included in a block if cancelling andequalization are repeated without cancelling the desired signals. On theother hand, if the residual Q after the canceling of all replicas isinput, the residual can be equally treated in the block, and thereforeall weights can be calculated with one inverse matrix calculation withrespect to the block. For this reason, the replica is independentlyinput and reconfigured to decrease the amount of the inversecalculation. However, a replica of the firstly received signal cannot begenerated. In this case, the reception-data vector (R) passes throughthe canceller 1115 as it is.

The signal output from the canceller 1114 is input to the signalequalizing-and-demultiplexing unit 1115, and then subjected toequalization using frequency-domain signals. When the repeated operationis performed, the signal equalizing-and-demultiplexing unit 1115performs, with use of an expression (104), MMSE equalization on eachsignal generated by a replica of the received signal for each datavector transmitted from the antennas 1 and 2 shown in FIG. 43 beingadded to the output (Q) of the canceller. FIG. 43 illustrates, as anexample of subcarrier selection, a case where subcarriers 1, 2, and 4are transmitted from the antennas 1 and 2.z=(1+γ_(Tn)δ_(Tn))⁻¹[γ_(Tn) s′ _(Tn) +F ^(H)Ψ_(Tn) Q]  (104)

Tn (n=1, 2 in the above case) denotes a transmission antenna. γ_(Tn) andδ_(Tn) denote real numbers used when tap coefficients are calculated.Similarly, Ψ_(Tn) denotes a complex square matrix having a size of theDFT block length, which is used when tap coefficients are calculated.s′_(Tn) denotes a replica of the signal transmitted from the antenna Tn.Q denotes a result (residual) of subtracting replicas of all thereceived signals from the received signals. Since a replica of areceived signal cannot be generated (s′_(Tn) is a zero vector) in thefirst operation, the signal R output from the canceller 1114 withoutbeing subjected to subtraction is subjected to equalization. Whencalculating Ψ_(Tn) and the like shown in the expression (104), channelmatrices Ξ_(n) and Ξ_(n) corresponding to the transmission-data vectors1 and 2 are used in addition to the channel matrix shown in theexpression (102). Ξ_(T1) and Ξ_(T2) are channel matrices for respectivetransmission antennas, which are used for equalizing thetransmission-data vectors 1 and 2.

$\begin{matrix}{\Xi_{T\; 1} = \begin{bmatrix}{\;{\Xi_{\; 11}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 11}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 11}\;(4)}} \\{\;{\Xi_{\; 21}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 21}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 21}\;(4)}}\end{bmatrix}} & (105) \\{\Xi_{T\; 2} = \begin{bmatrix}{\;{\Xi_{\; 12}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 12}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 12}\;(4)}} \\{\;{\Xi_{\; 22}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 22}\;(2)}} & 0 & 0 \\0 & 0 & 0 & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 22}\;(4)}}\end{bmatrix}} & (106)\end{matrix}$

By the equalization with use of the expression (104), the equalizedtime-domain signals are output from the signalequalizing-and-demultiplexing unit 1115 for each transmission data (see,for example, Non-Patent Document 3).

The signals that have been transmitted from the respective transmissionantennas and equalized for the respective signals are input to the DFTunits 1116 and 1117, converted into frequency-domain signals by the DFTunits 1116 and 1117, and then input to the spectral demapping unit 1118.The spectral demapping unit 1118 performs demapping common to spectratransmitted from the antennas 1 and 2 based on spectral mappinginformation. Then, the demapped signals are converted into time-domainsignals by the IDFT units 1119 and 1120, converted into serial signalsby the P/S converters 1121 and 1122, and then subjected to demodulationand decoding.

The demodulators 1123 and 1124 calculate LLRs (Log Likelihood Ratios)indicative of the reliability of the reception data subjected to errorcoding. The decoders 1125 and 1126 perform error correction decoding onthe LLRs to update the LLRs. The repetition controllers 1127 and 1128receiving the LLRs determine whether or not the repeated operation hasbeen performed the predetermined number of times. If the repeatedoperation has been performed the predetermined number of times, therepetition controllers 1127 and 1128 output the LLRs to the determiningunits 1129 and 1130. On the other hand, if the repeated operation hasnot yet been performed the predetermined number of times, the repetitioncontrollers 1127 and 1128 output the LLRs to the replica generators 1131and 1132, and proceeds to a process of generating replicas of receivedsignals. Assuming that a CRC (Cyclic Redundancy Check) is used, therepeated operation may end if no error is detected.

The replica generators 1131 and 1132 generate signal replicas (replicasof transmitted signals) corresponding to the respective LLRs. Thegenerated replicas are passed through the S/P converters 1133 and 1134,and then converted by the DFT units 1135 and 1136 into frequency-domainreplicas of signals transmitted from the respective antennas.

Then, the frequency-domain signal replicas generated in this manner aremapped by the spectral mapping unit 1137 based on mapping informationreceived from a spectrum determining unit (not shown) in a similarmanner as done on the transmitting side. Then, the replicas S′ subjectedto the spectral mapping are input to the channel multiplier 1140, andthen input to the signal equalizing-and-demultiplexing unit 1115 throughthe IDFT units 1138 and 1139. The signal equalizing-and-demultiplexingunit 1115 receiving the replicas S′ subjected to the spectral mappingreconfigures the received signals of the transmission-data vectors 1 and2 using the replicas as explained above, and uses the reconfiguredreceived signals for equalizing the respective transmission-datavectors. To generate replicas of the received signals to be used forsubtraction from the received signals performed by the canceller 1114,the channel multiplier 1140 multiplies the replicas subjected to thespectral mapping by the channel matrix (Ξ shown in the expression(102)). Then, the replicas (ΞS′) of the received signals, which areoutput from the channel multiplier 1140, are input to the canceller1114, and then subtraction shown in the expression (100) is performed asexplained above.

The reception device shown in FIG. 42 repeats a series of operations,such as the cancelling of replicas, the equalization, the spectrumdemapping, the decoding, and the generation of replicas, and therebygradually increases the reliability of the decoded bits. After theseries of operations are performed the predetermined number of times,the determining units 207 and 208 perform hard determination on bits,and then the transmission data are reproduced as decoded data.

As a system for multiplexing transmission data pieces transmitted frommultiple transmission stations with use of SC-ASA, an FDMA (FrequencyDivision Multiple Access)-based system has been also proposed in whichthe point number of IDFT (Inverse Discrete Fourier Transform) is set bythe transmission station to be greater than that of DFT, and subcarriersadded null data are used by another transmission station (see, forexample, Non-Patent Document 3).

FIGS. 44A and 44B are schematic block diagrams illustratingconfigurations of a transmission station device and a reception stationdevice when user multiplexing is performed by two conventionaltransmission stations with use of SC-ASA. Regarding the transmissiondevice shown in FIG. 44A, two pieces of transmission data 1 and 2 areencoded by the encoders A1000-1 and A1000-2, and the encodedtransmission data pieces are modulated by modulators A1001-1 andA1001-2, respectively. The signals modulated by the modulators A1001-1and A1001-2 are converted into parallel signals by the S/P convertersA1002-1 and A1002-2, and then converted into frequency-domain signals byDFT units A1003-1 and A1003-2. Then, the frequency-domain signals aremapped by the spectral mapping units A1004-1 and A1004-2 so that thetransmission data 1 and 2 are not transmitted using the same frequencysubcarriers. In this case, the frequency-domain signals are mapped ontosubcarriers that have good SNR (Signal to Noise Ratio) or SNIR (Signalto Noise Interference Ratio) and have frequencies not used by otherusers.

The mapped frequency-domain transmitted signals are converted intotime-domain signals by IDFT units A1005-1 and A1005-2, and thenconverted into serial signals by the P/S converters A1006-1 and A1006-2.Then, cyclic prefixes are inserted into the serial signals by the CP(Cyclic Prefix) inserter A1007-1 and A1007-2. Then, the serial signalsare converted into analog signals by the D/A converters A1008-1 andA1008-2. Finally, the analog signals are upconverted into radiofrequency signals by radio units A1009-1 and A1009-2, and transmittedfrom transmission antennas 1010-1 and 1010-2.

Regarding the reception device shown in FIG. 44B, a received signalgenerated by multiplexing two signals simultaneously transmitted isreceived by a reception antenna 1100. Then, the received signal isdownconverted by a radio unit A1111. The downconverted received signalis converted into a digital signal by an A/D converter A1101. Then, acyclic prefix is removed from the digital signal by a CP (Cyclic Prefix)remover A1102. Then, the digital signal from which the cyclic prefix hasbeen removed is converted into parallel signals by the S/P converterA1103. The parallel digital signals are converted into frequency-domainsignals by a DFT unit A1104. Then, subcarriers of the respectivefrequency-domain signals are reversely allocated, and therebyfrequency-domain signals transmitted from the respective transmissionstations are demultiplexed. Then, the frequency-domain signals areindependently equalized for the respective pieces of transmission databy signal equalizers A1106-1 and A1106-2, and then converted intotime-domain signals by IDFT units A1107-1 and A1107-2. Then, thetime-domain signals are converted into serial signals by P/S convertersA1108-1 and A1108-2, and then demodulated by demodulators A1109-1 andA1109-2. Thus, decoded data 1 and 2 transmitted from the respectivetransmission stations are obtained from decoders A1110-1 and 1110-2.

As an equalization method performed by the signal equalizer A1106, MMSE(Minimum Mean Square Error)-based equalization is used. Generally, a tapminimizing an evaluation function J shown in an expression (107) iscalculated in MMSE equalization.J=E[|W ^(H) r−S| ²]  (107)

In an expression (107), E[x] denotes a mean value of x. W denotes acomplex tap matrix including column vectors each being an optimal tapvector for each symbol included in DFT-S-OFDM symbols. r denotes acomplex-time-domain received signal vector. s denotes a time-domaintransmitted signal vector. A^(H) denotes a Hermitian transpose of amatrix A. In this case, an optimal tap coefficient W is called a Wienersolution expressed by an expression (108).W=H(HH ^(H)+σ² I)⁻¹  (108)

In the expression (108), H denotes a time-domain channel matrix. σ²denotes noise variance. I denotes a unit matrix. Particularly when afrequency-domain signal operation is performed, a matrix having diagonalelements identical to frequency responses calculated by use of Fouriertransform from channel impulse responses may be used as a channelmatrix. Therefore, when frequency-domain received signals are used, thetap coefficients expressed by the expression (108) can be transformed asthe following expression (109) where Ξ denotes channel frequencyresponses.W=F ^(H)Ξ(ΞΞ^(H)+σ² I)⁻¹ F  (109)

In the expression (109), F denotes a matrix for performing DFT and F^(H)denotes a matrix for performing inverse DFT. When a time-domain receivedsignal r is multiplied by the tap matrix, the equalized received signalz can be expressed as an expression (110).z=F ^(H)Ξ(ΞΞ^(H)+σ² I)⁻¹ Fr=F ^(H)Ξ(ΞΞ^(H)+σ² I)⁻¹ R  (110)

In the above expression, R=Fr, i.e., R denotes the received signal rconverted by DFT into a frequency-domain signal. According to theexpression (110), when a normal received signal is input and equalizedin the frequency domain, the received signal is converted by DFT,multiplied by a Hermitian transpose of a matrix obtained by removingboth F^(H) and F of the expression (109), and then converted by IDFTinto a time-domain signal again. Accordingly, a normal MMSE filterreceives a frequency-domain received signal and a channel frequencyresponse, and outputs a signal equalized in the frequency domain.

On the other hand, when a reception device is configured to include acanceller, such as SC/MMSE (Soft Canceller followed by MMSE), whichperforms repeated operation, interference waves are cancelled fromreceived signals by use of replicas of signals generated based on thereliability of bits received from the decoder, and thereby the precisionof signals input to the equalizer. Accordingly, signals input to theequalizer differ for each repletion operation. For this reason, the termcorresponding to the received signal r of the evaluation functionexpressed by the expression (107) becomes one generated by signals otherthan desired signals being cancelled. Therefore, the equalized signalcan be expressed as an expression (111).z=(1+γδ)⁻¹ [γs _(rep)(k)+F ^(H) ΨR _(rest)]  (111)

In the expression (111), R_(rest) denotes a residual that remainswithout being cancelled and is generated by subtracting, from actualtime-domain received signals, replicas of the received signals generatedby multiplying replicas of the time-domain signals by channelcharacteristics. s_(rep)(k) denotes a replica of a transmitted signalfor the k-th sample. γ and δ are real numbers used when tap coefficientsare calculated. Similarly, Ψ denotes a complex square matrix having thesize of the DFT-S-OFDM symbol length, which is used when tapcoefficients are calculated. These are calculated by use of thefrequency-domain channel characteristics and the replicas offrequency-domain signals (see, for example, Non-Patent Document 2).Since a replica is not input in the first operation in the expression(111) (i.e., s_(rep)(k)=0), this case is a case of the optimal tap inthe expression (107), and therefore the expression (111) becomesidentical to the expression (109).

Accordingly, in the case of SC/MMSE equalization, a frequency-domainresidual is input as an input signal, a replica of a time-domain signaland frequency-domain channel characteristics are input, and then atime-domain signal is output. As shown in the expression (111), theoperation of canceling elements other than desired elements is performedby firstly calculating the residual R_(rest), and then reconfiguring thedesired elements by use of the replicas of the transmitted signals andthe channel characteristics. Consequently, the desired elements can beuniquely expressed among the DFT-S-OFDM symbols. Further, the sameresidual R_(rest) can be used for the DFT-S-OFDM symbols, therebyenabling a reduction in the amount of calculation including inversematrix calculation.

-   [Non-Patent Document 1] “A Study on Broadband Single Carrier    Transmission Technique using Dynamic Spectrum Control,” RCS 2006,    January 2007.-   [Non-Patent Document 2] M. Tuchler and J. Hagenauer, “Linear time    and frequency domain turbo equalization,” Proc. VTC, pp. 2773-2777,    Rhodes, Greece, October 2001.-   [Non-Patent Document 3] “A Study on Dynamic Spectrum Control based    Co-Channel Interference Suppression Technique for Multi-User MIMO    Systems,” Proceedings of the IEICE General Conference in 2006,    March, 2007.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Regarding the conventional multi-user or single-user MIMO, as explainedabove, transmission has been performed from multiple antennas usingselected frequencies. In this case, control has been performed such thatall channels between multiple transmission systems and multiplereception systems are considered, and subcarriers having relatively goodchannel conditions among the considered channels are used (or users areallocated). Specifically, in a case of 2×2 MIMO transmission (which maybe any one of multi-user and single-user MIMO) including transmissionantennas Tx1 and Tx2 and reception antennas Rx1 and Rx2, all of fourchannels H11, 1121, H12, and H22 are considered, subcarriers havingrelatively good channel conditions are selected for both transmissionantennas Tx1 and Tx2, and then different data is simultaneouslytransmitted from the transmission antennas Tx1 and Tx2. This is becausesignals transmitted from multiple transmission antennas interfere withone another in the case of MIMO transmission, and therefore all channelshave to be considered to select subcarriers having good conditions.

When SC-ASA is adapted to the MIMO transmission, however, a selection bysuch a control does not achieve the highest diversity effect, therebycausing a problem that excellent frequency utilization efficiency cannotbe achieved. In other words, SC-ASA is generally a scheme in whichoptimal subcarriers are selected for each transmission device(transmission antenna), and then the selected subcarriers aretransmitted, thereby achieving a high diversity effect and thereforeenhancing the frequency utilization efficiency. When SC-ASA is adaptedto the conventional MIMO transmission (multi-user or single user MIMO)as explained above, optimal subcarriers are not selected independentlyfor each transmission antenna, thereby causing a problem that excellentfrequency utilization efficiency cannot be achieved.

Conventionally, when transmission is performed by multiple transmissiondevices using SC-ASA, subcarriers are allocated to the transmissiondevices so that the same frequency is not used by two or moretransmission devices. For this reason, even if subcarriers have goodreceived SNR or SINR for one transmission device, and if the subcarriershave been already allocated to another transmission device, the formertransmission device cannot use the subcarriers. Thus, even ifsubcarriers having good received SNR or SINR are included in atransmittable band, and if the subcarriers are used by another device,the subcarriers cannot be used, thereby causing a decrease in thefrequency utilization efficiency and causing a problem that excellentfrequency utilization efficiency cannot be achieved.

A problem to be solved is that excellent frequency utilizationefficiency has to be achieved even when SC-ASA is adapted totransmission from multiple transmission devices or MIMO transmission.

Means for Solving the Problems

(1) A radio communication system of the present invention includes: atransmission device including a plurality of transmission antennas fortransmitting a transmitted signal which is subjected to frequencyspreading and allocated onto subcarriers; and a reception deviceincluding a plurality of reception antennas for receiving thetransmitted signal. The subcarriers transmitted from each of theplurality of transmission antennas are independently determined based ona channel capacity for each of the subcarriers transmitted between eachof the plurality of transmission antennas and each of the plurality ofreception antennas or on a value corresponding to the channel capacity.

(2) A radio communication system of the present invention includes: aplurality of first radio communication devices; and a second radiocommunication device that communicates with the plurality of first radiocommunication devices. Each of the first radio communication devicesincludes: a frequency spreading unit that performs frequency spreadingon a transmitted signal to generate a frequency spread signal; and amapping unit that allocates the frequency spread signal onto subcarriersbased on mapping information for specifying the subcarriers. The secondradio communication device includes: a demapping unit that extracts asignal corresponding to the subcarriers specified by the mappinginformation from received signals; and an inverse frequency-spreadingunit that performs inverse frequency spreading on the signal extracted.Any one of the first and second radio communication devices includes asubcarrier determining unit that determines, based on a channel capacityfor each of subcarriers transmitted from each of a plurality oftransmission antennas used by a corresponding one of the plurality ofthe first radio communication devices or a value corresponding to thechannel capacity, subcarriers onto which the frequency spread signal tobe transmitted from the plurality of transmission antennas is allocated,and generates the mapping information specifying the determinedsubcarriers.

(3) Regarding the radio communication system, each of the plurality offirst radio communication devices includes: a cyclic prefix inserterthat adds a cyclic prefix to the signal allocated by the mapping unitonto the subcarriers.

(4) Regarding the radio communication system, some overlappingsubcarriers of the subcarriers determined by the subcarrier determiningunit are allocated to the plurality of transmission antennas.

(5) Regarding the radio communication system, each of the first radiocommunication devices comprises a plurality of antennas, and thesubcarrier determining unit generates mapping information specifyingsubcarriers to be transmitted from each of the plurality of antennas.

(6) Regarding the radio communication system, the subcarrier determiningunit sets the number of the overlapping subcarriers allocated to theplurality of transmission antennas to be equal to or less than thenumber of reception antennas used by the second radio communicationdevice.

(7) Regarding the radio communication system, the channel capacity is achannel capacity C_(m)(k) for each of subcarriers transmitted from eachof the plurality of transmission antennas, the channel capacity C_(m)(k)being expressed as:

${C_{m}(k)} = {\log_{2}\left( {1 + {\frac{E_{S}}{N_{T}}{\xi_{m}^{H}(k)}{\xi_{m}(k)}\Sigma_{m}^{- 1}\;(k)}} \right)}$where m is the transmission antenna number, k is the subcarrier number,N_(T) is the number of the plurality of transmission antennas, E_(S) istransmission energy of one of the plurality of first radio communicationdevices, ξ_(m)(k) is a channel vector corresponding to a k-th subcarriertransmitted from an m-th transmission antenna, and Σ_(m)(k) isinterference noise power corresponding to the k-th subcarriertransmitted from the m-th transmission antenna.

(8) Regarding the radio communication system, the value corresponding tothe channel capacity is a ratio of received signal power tointerference-and-noise power for each of subcarriers transmitted fromeach of the plurality of transmission antennas.

(9) Regarding the radio communication system, the second radiocommunication device includes: a channel estimator that performs channelestimation with respect to a channel between each of the plurality oftransmission antennas used by the corresponding one of the plurality ofthe first radio communication devices and each of a plurality ofreception antennas used by the second radio communication device; achannel reconfiguring unit that extracts, from channel estimationresults obtained by the channel estimator, channel estimation resultscorresponding to the subcarriers specified by the mapping information;and an equalizer that equalizes a signal based on the channel estimationresults extracted by the channel reconfiguring unit, and the inversefrequency-spreading unit performs inverse frequency spreading on thesignal that is equalized by the equalizer and extracted by the demappingunit.

(10) Regarding the radio communication system, the channel reconfiguringunit generates, for each of the subcarriers specified by the mappinginformation, a virtual-subchannel estimation result that is acombination of channel estimation results each corresponding to one ofthe plurality of transmission antennas used by the corresponding one ofthe plurality of the first radio communication devices, the channelestimation results combined being extracted from the channel estimationresults obtained by the channel estimator.

(11) Regarding the radio communication system, the channel reconfiguringunit generates, for each of the plurality of transmission antennas usedby the corresponding one of the plurality of the first radiocommunication devices, a virtual subchannel including a group ofsubcarriers transmitted from the plurality of transmission antennas, andextracts a virtual-subchannel estimation result.

(12) Regarding the radio communication system, the channel reconfiguringunit generates a plurality of virtual-subchannel estimation results, thenumber of which equals the number of reception antennas used by thesecond radio communication device.

(13) Regarding the radio communication system, the channel reconfiguringunit combines a plurality of virtual-subchannel estimation results togenerate a virtual-subchannel estimation result to be used forequalization performed by the equalizer.

(14) Regarding the radio communication system, each of the plurality offirst radio communication devices includes: an encoder that performserror correction coding on transmission data; and the frequencyspreading unit that performs frequency spreading on a transmitted signalsubjected to the error correction coding performed by the encoder togenerate a frequency spread signal. The second radio communicationdevice includes: a decoder that performs error correction decoding onthe signal subjected to the inverse frequency spreading performed by theinverse frequency-spreading unit; a replica generator that generates areplica of the transmitted signal based on a result of the errorcorrection decoding performed by the decoder; a replicafrequency-spreading unit that performs frequency spreading on thereplica of the transmitted signal to generate a replica of thefrequency-spread signal; a replica mapping unit that generates, from thereplica of the frequency-spread signal, a received signal replica foreach of virtual subchannels combined by the channel reconfiguring unit;a canceller that cancels interference elements from the received signalsusing the received signal replica for each of the virtual subchannelscombined by the channel reconfiguring unit; and a repetition controllerthat controls the repeated number of repeated operations includingoperations of the equalizer, the demapping unit, the inversefrequency-spreading unit, the decoder, the replica generator, thereplica frequency-spreading unit, the replica mapping unit, and thecanceller.

(15) Regarding the radio communication system, the canceller cancels theinterference elements by subtracting replicas of all the receivedsignals from the received signals and then adding the received signalreplica of a desired one of the virtual subchannels to a result of thesubtraction.

(16) Regarding the radio communication system, the equalizer uses, basedon the repeated number, a different virtual subchannel to perform therepeated operations.

(17) Regarding the radio communication system, when the equalizer uses adifferent virtual subchannel based on the repeated number, the equalizerpreferably uses, in a second-or-later repeated operation, a virtualsubchannel identical to a channel including a combination of subcarriersused by the plurality of transmission antennas.

(18) Regarding the radio communication system, if the number ofoverlapping subcarriers of the subcarriers determined by the subcarrierdetermining unit, the overlapping subcarriers being allocated to theplurality of transmission antennas used by the plurality of the firstradio communication devices, is greater than the number of the pluralityof reception antennas used by the second radio communication device, thechannel reconfiguring unit generates different virtual-subchannelestimation results, the number of the different virtual-subchannelestimation results equaling the number of the overlapping subcarriers.

(19) A radio communication method of the present invention is a radiocommunication method for a radio communication system including aplurality of first radio communication devices, and a second radiocommunication device communicating with the plurality of first radiocommunication devices. The radio communication method includes: a firststep of the first or second radio communication device determining,based on a channel capacity for each of subcarriers transmitted fromeach of a plurality of transmission antennas used by a corresponding oneof the plurality of first radio communication devices or on a valuecorresponding to the channel capacity, subcarriers onto which afrequency spread signal to be transmitted from the corresponding one ofthe plurality of transmission antennas is allocated, and generates themapping information specifying the determined subcarriers; a second stepof the first radio communication device performing frequency spreadingon a transmitted signal to generate a frequency spread signal; a thirdstep of the first radio communication device allocating the frequencyspread signal onto subcarriers based on mapping information forspecifying the subcarriers, and transmitting the subcarriers; a fourthstep of the second radio communication device extracting a signalcorresponding to the subcarriers specified by the mapping informationfrom received signals; and a fifth step of the second radiocommunication device performing inverse frequency spreading on thesignal extracted.

(20) A radio communication device of the present invention includes: asubcarrier determining unit that determines, based on a channel capacityfor each of subcarriers transmitted from each of a plurality oftransmission antennas or on a value corresponding to the channelcapacity, subcarriers onto which a frequency spread signal to betransmitted from each of the plurality of transmission antennas isallocated, and generates the mapping information specifying thesubcarriers determined; a frequency spreading unit that performsfrequency spreading on a transmitted signal to generate the frequencyspread signal; and a mapping unit that allocates the frequency spreadsignal onto the subcarriers based on the mapping information.

(21) A program of the present invention has a computer included in aradio communication device function as: a subcarrier determining unitthat determines, based on a channel capacity for each of subcarrierstransmitted from each of a plurality of transmission antennas or on avalue corresponding to the channel capacity, subcarriers onto which afrequency spread signal to be transmitted from each of the plurality oftransmission antennas is allocated, and generates mapping informationspecifying the subcarriers determined; a frequency spreading unit thatperforms frequency spreading on a transmitted signal to generate thefrequency spread signal; and a mapping unit that allocates the frequencyspread signal onto the subcarriers based on the mapping information.

(22) A radio communication device of the present invention communicateswith a plurality of other radio communication devices each transmittinga frequency spread signal allocated onto subcarriers. The radiocommunication device includes: a subcarrier determining unit thatdetermines, based on a channel capacity for each of subcarrierstransmitted from each of a plurality of transmission antennas used bythe plurality of other radio communication devices or on a valuecorresponding to the channel capacity, subcarriers onto which afrequency spread signal to be transmitted from each of the plurality oftransmission antennas is allocated, and generates the mappinginformation specifying the determined subcarriers; a demapping unit thatextracts a signal corresponding to the subcarriers specified by themapping information from received signals; and an inversefrequency-spreading unit that performs inverse frequency spreading onthe signal extracted.

(23) A program of the present invention has a computer, which isincluded in a radio communication device communicating with a pluralityof other radio communication devices each transmitting a frequencyspread signal allocated onto subcarriers, function as: a subcarrierdetermining unit that determines, based on a channel capacity for eachof subcarriers transmitted from each of a plurality of transmissionantennas used by the plurality of other radio communication devices oron a value corresponding to the channel capacity, subcarriers onto whicha frequency spread signal to be transmitted from each of the pluralityof transmission antennas is allocated, and generates mapping informationspecifying the determined subcarriers; a demapping unit that extracts asignal corresponding to the subcarriers specified by the mappinginformation from received signals; and an inverse frequency-spreadingunit that performs inverse frequency spreading on the signal extracted.

(24) A radio communication system of the present invention includes: aplurality of transmission devices each including a plurality oftransmission antennas for transmitting a transmitted signal which issubjected to frequency spreading and allocated onto subcarriers; and areception device including a plurality of reception antennas forreceiving the transmitted signal. The subcarriers for transmitting thefrequency spread signal are independently selected based on a channelcapacity for each of the subcarriers transmitted between each of theplurality of transmission antennas and each of the plurality ofreception antennas or on a value corresponding to the channel capacity,so that some overlapping subcarriers of the subcarriers are allocated tothe plurality of transmission devices.

(25) A radio communication system of the present invention includes: aplurality of transmission devices each transmitting a transmitted signalwhich is subjected to frequency spreading and allocated ontosubcarriers; and a reception device receiving the transmitted signal.Each of the plurality of transmission devices allocates the frequencyspread signal onto the subcarriers such that some overlappingsubcarriers of the subcarriers are allocated to the plurality oftransmission devices.

(26) A radio communication system of the present invention includes: aplurality of transmission devices each transmitting a transmitted signalwhich is subjected to frequency spreading and allocated ontosubcarriers; and a reception device receiving the transmitted signal.Each of the plurality of transmission devices includes: an encoder thatperforms error correction coding on transmission data to generateencoded data; a frequency spreading unit that performs frequencyspreading on a signal generated from the encoded data to generate afrequency spread signal; a spectral mapping unit that allocates thefrequency spread signal onto subcarriers based on spectrum allocationinformation specifying subcarriers onto which each of the plurality oftransmission devices allocates the frequency spread signal, the spectrumallocation information indicating that some overlapping subcarriers ofthe subcarriers are allocated to the plurality of transmission devices.The reception device includes a spectral demapping unit that extracts,based on the spectrum allocation information, a signal corresponding tothe subcarriers onto which each of the plurality of transmission devicesallocates the frequency spread signal from the transmitted signalreceived.

(27) Regarding the radio communication system, the reception deviceincludes: a signal canceller that cancels, from the signal extracted bythe spectral demapping unit, at least replicas of the transmittedsignals interfering with a desired one of the transmitted signals; anequalizer that detects the transmitted signal transmitted by acorresponding one of the plurality of transmission devices from anoutput of the signal canceller; a demodulator that extracts informationconcerning the encoded data from the transmitted signal detected; adecoder that performs error correction decoding on the informationextracted and updates the information; and a replica generator thatgenerates replicas of the transmitted signals based on the informationupdated.

(28) Regarding the radio communication system, each of the plurality oftransmission devices further includes: an inverse time-frequencyconverter that converts the frequency spread signal allocated by thespectral mapping unit onto the subcarriers into a time signal; and acyclic prefix inserter that adds a cyclic prefix to the time signalconverted by the inverse time-frequency converter. The reception devicefurther includes: a cyclic prefix remover that extracts a valid signalfrom the transmitted signals received; and a time-frequency converterthat performs time-to-frequency conversion on the valid signal extractedby the cyclic prefix remover. The spectral demapping unit extracts asignal corresponding to the subcarriers onto which each of the pluralityof transmission devices allocates the frequency spread signal from thevalid signal converted by the time-frequency converter.

(29) Regarding the radio communication system, each of the plurality oftransmission devices further includes: a first interleaver that arrangesthe encoded data generated by the encoder. The reception device furtherincludes: a deinterleaver that returns the arrangement of theinformation concerning the encoded data, which is extracted by thedemodulator, in a reverse order of the arrangement performed by thefirst interleaver; and a second interleaver that arranges the updatedinformation concerning the encoded data in the same order of thearrangement performed by the first interleaver.

(30) Regarding the radio communication system, the reception deviceincludes: a spectrum-allocation determining unit that determinesallocation of subcarriers for each of the plurality of transmissiondevices, and generates spectrum allocation information indicatingresults of the determination; and a transmitter that transmits thespectrum allocation information. Each of the plurality of thetransmission devices includes: a receiver that receives the spectrumallocation information transmitted from the reception device.

(31) Regarding the radio communication system, the frequency spreadingis performed by Fourier transform to convert the transmitted signal thatis a time-domain signal into a frequency signal.

(32) Regarding the radio communication system, the frequency spreadingis performed by multiplying the transmitted signal by a spreading code.

(33) Regarding the radio communication system, at least one of anencoding rate, a modulation scheme, and a transmission power differs foreach of the plurality of the transmission devices.

(34) Regarding the radio communication system, the maximum value of arate of the overlapping subcarriers is determined based on asignal-to-noise ratio measured by the reception device.

(35) Regarding the radio communication system, each of the transmissiondevices performs transmission using the overlapping subcarriers havingthe rate equal to or less than the maximum value.

(36) Regarding the radio communication system, the spectrum-allocationdetermining unit that changes the allocation of subcarriers for each ofthe plurality of transmission devices at a predetermined time interval.

(37) A reception device of the present invention communicates with aplurality of transmission devices each of which performs frequencyspreading on a transmitted signal generated from encoded data generatedby performing error correction coding on information data, and allocatesthe frequency spread signal onto subcarriers to be transmitted so thatsome overlapping subcarriers of the subcarriers are allocated to theplurality of transmission devices. The reception device includes: atime-frequency converter that performs time-to-frequency conversion onreceived signals; a spectral demapping unit that extracts, from thereceived signals, a signal corresponding to the subcarriers onto whicheach of the plurality of the transmission devices allocates thefrequency spread signal based on spectrum allocation informationspecifying subcarriers onto which the frequency spread signal is to beallocated; a signal canceller that cancels, from the signal extracted bythe spectral demapping unit, at least replicas of the transmittedsignals interfering with a desired one of the transmitted signals; anequalizer that detects the transmitted signal transmitted by acorresponding one of the plurality of transmission devices from anoutput of the signal canceller; a demodulator that extracts informationconcerning the encoded data from the transmitted signal detected; adecoder that performs error correction decoding on the informationextracted and updates the information; and a replica generator thatgenerates replicas of the transmitted signals based on the informationupdated.

(38) A reception device of the present invention communicates with aplurality of transmission devices each of which performs frequencyspreading on a transmitted signal generated from encoded data generatedby performing error correction coding on information data, allocates thefrequency spread signal onto subcarriers to be transmitted with a cyclicprefix added so that some overlapping subcarriers of the subcarriers areallocated to the plurality of transmission devices. The reception deviceincludes: a cyclic prefix remover that extracts a valid signal fromreceived signals; a time-frequency converter that performstime-to-frequency conversion on the valid signal extracted by the cyclicprefix remover; a spectral demapping unit that extracts a signalcorresponding to the subcarriers onto which each of the plurality oftransmission devices allocates the frequency spread signal from thevalid signal converted by the time-frequency converter based on spectrumallocation information specifying subcarriers to which the frequencyspread signal is to be allocated; a signal canceller that cancels, fromthe signal extracted by the spectral demapping unit, at least replicasof the transmitted signals interfering with a desired one of thetransmitted signals; an equalizer that detects the transmitted signaltransmitted by a corresponding one of the plurality of transmissiondevices from an output of the signal canceller; a demodulator thatextracts information concerning the encoded data from the transmittedsignal detected; a decoder that performs error correction decoding onthe information extracted and updates the information; and a replicagenerator that generates replicas of the transmitted signals based onthe information updated.

(39) A reception device of the present invention communicates with aplurality of transmission devices each of which performs errorcorrection coding on transmission data, interleaves the encoded data togenerate a transmitted signal, performs frequency spreading on thetransmitted signal, and allocates the frequency spread signal ontosubcarriers to be transmitted so that some overlapping subcarriers ofthe subcarriers are allocated to the plurality of transmission devices.The reception device includes: a time-frequency converter that performstime-to-frequency conversion on received signals; a spectral demappingunit that extracts a signal corresponding to the subcarriers onto whicheach of the plurality of transmission devices allocates the frequencyspread signal from the received signals converted by the time-frequencyconverter based on spectrum allocation information specifyingsubcarriers to which the frequency spread signal is to be allocated; asignal canceller that cancels, from the signal extracted by the spectraldemapping unit, at least replicas of the transmitted signals interferingwith a desired one of the transmitted signals; an equalizer that detectsthe transmitted signal transmitted by a corresponding one of theplurality of transmission devices from an output of the signalcanceller; a demodulator that extracts information concerning theencoded data from the transmitted signal detected; a deinterleaver thatreturns arrangement of the information concerning the encoded data,which is extracted by the demodulator, in a reverse order of theinterleaving performed by each of the plurality of transmission devices;a decoder that performs error correction decoding on the information,the arrangement of which is returned by the deinterleaver, and updatesthe information; and a replica generator that generates replicas of thetransmitted signals based on the information concerning the encoded datainterleaved by each of the plurality of transmission devices.

(40) Regarding any one of the above reception devices, the informationconcerning the encoded data is reliability of the encoded data, and thereplica generator generates replicas based on the reliability of theencoded data.

(41) Any one of the above reception devices further includes arepetition controller that controls repeated operations includinggeneration of replicas performed by the replica generator and cancellingof interfering replica signals performed by the canceller.

(42) Regarding the reception device, the equalizer changes thetransmitted signal to be equalized based on the repeated number oftimes.

(43) Regarding the reception device, the equalizer preferentiallyequalizes the transmitted signal that is easy to be detected.

(44) Regarding any one of the above reception devices, the replicagenerator generates replicas of interfering transmitted signals asfrequency-domain signals, and the signal canceller cancels at least thereplicas of the interfering transmitted signals from the signalextracted by the spectral demapping unit.

(45) Regarding any one of the above reception devices, the replicagenerator generates replicas of interfering transmitted signals astime-domain signals, and the signal canceller cancels at least thereplicas of the interfering transmitted signals from the receivedsignals subjected to the time-to-frequency conversion.

(46) Any one of the above reception devices further includes aninterference spectrum selector that generates replicas of interferingtransmitted signals.

(47) A program of the present invention has a computer, which isincluded in a reception device communicating with a plurality oftransmission devices each of which performs frequency spreading on atransmitted signal generated from encoded data generated by performingerror correction coding on information data, allocates the frequencyspread signal onto subcarriers to be transmitted so that someoverlapping subcarriers of the subcarriers are allocated to theplurality of transmission devices, function as: a time-frequencyconverter that performs time-to-frequency conversion on receivedsignals; a spectrum demapping unit that extracts, from the receivedsignals, a signal corresponding to the subcarriers onto which each ofthe plurality of the transmission devices allocates the frequency spreadsignal based on spectrum allocation information specifying subcarriersonto which the frequency spread signal is to be allocated; a signalcanceller that cancels, from the signal extracted by the spectraldemapping unit, at least replicas of the transmitted signals interferingwith a desired one of the transmitted signals; an equalizer that detectsthe transmitted signal transmitted by a corresponding one of theplurality of transmission devices from an output of the signalcanceller; a demodulator that extracts information concerning encodeddata from the transmitted signal detected; a decoder that performs errorcorrection decoding on the information extracted and updates theinformation; and a replica generator that generates replicas of thetransmitted signals based on the information updated.

(48) A radio communication method of the present invention is a radiocommunication method for a radio communication system including aplurality of transmission devices each transmitting subcarriers ontowhich a transmitted signal subjected to frequency spreading isallocated, and a reception device receiving the transmitted signal. Eachof the plurality of transmission devices allocates the frequency spreadsignal onto the subcarriers such that some overlapping subcarriers ofthe subcarriers are allocated to the plurality of transmission devices.

Effects of the Invention

According to the present invention, even when SC-ASA is adapted totransmission from multiple transmission devices or MIMO transmission,adequate subcarriers can be selected, and thereby excellent frequencyutilization efficiency can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart indicative of a control flow illustrating a methodof selecting subcarriers to be used for transmission of data accordingto a first embodiment of the present invention.

FIG. 2 illustrates an example result of subcarrier selection accordingto the first embodiment.

FIG. 3 is a schematic block diagram illustrating a configuration of amobile station device 500 according to the first embodiment.

FIG. 4 illustrates operations of mapping units 5-1 and 5-2 according tothe first embodiment.

FIG. 5 is a schematic block diagram illustrating a configuration of amobile station device 501 according to the first embodiment.

FIG. 6 is a schematic block diagram illustrating a configuration of abase station device 510 according to a second embodiment of the presentinvention.

FIG. 7 illustrates an example result of subcarrier selection accordingto the second embodiment.

FIG. 8 illustrates example information indicated by mapping informationaccording to the second embodiment.

FIG. 9 is a schematic block diagram illustrating a configuration of abase station device 511 according to the second embodiment.

FIG. 10 is a flowchart indicative of a control flow illustrating amethod of selecting subcarriers to be used for transmission of dataaccording to a third embodiment of the present invention.

FIG. 11 illustrates an example result of subcarrier selection accordingto the third embodiment.

FIG. 12 is a schematic block diagram illustrating a configuration of abase station device 512 according to the third embodiment.

FIG. 13 illustrates an example result of subcarrier selection andtransmission-data vectors targeted for equalization according to thethird embodiment.

FIG. 14 illustrates an example result of subcarrier selection accordingto a fourth embodiment of the present invention.

FIG. 15 is a schematic block diagram illustrating a configuration of abase station device 513 according to the fourth embodiment.

FIG. 16A illustrates subcarriers targeted for operations of an operationsystem 1 according to the fourth embodiment.

FIG. 16B illustrates subcarriers targeted for operations of an operationsystem 2 according to the fourth embodiment.

FIG. 17 illustrates data input to IDFT units 116 to 119 according to thefourth embodiment.

FIG. 18 illustrates outputs of DFT units 213 to 216 according to thefourth embodiment.

FIG. 19 is a schematic block diagram illustrating a configuration of abase station device 514 according to a fifth embodiment of the presentinvention.

FIG. 20A illustrates example subcarriers targeted for repeatedoperations corresponding to respective repeated number of times andallocation of virtual subcarriers at the time of the operation accordingto the fifth embodiment.

FIG. 20B illustrates example subcarriers targeted for repeatedoperations corresponding to respective repeated number of times andallocation of virtual subcarriers at the time of the operation accordingto the fifth embodiment.

FIG. 20C illustrates example subcarriers targeted for repeatedoperations corresponding to respective repeated number of times andallocation of virtual subcarriers at the time of the operation accordingto the fifth embodiment.

FIG. 20D illustrates example subcarriers targeted for repeatedoperations corresponding to respective repeated number of times andallocation of virtual subcarriers at the time of the operation accordingto the fifth embodiment.

FIG. 21A illustrates an example mapping of outputs after signalequalization-and-demultiplexing according to the fifth embodiment.

FIG. 21B illustrates an example mapping of outputs after signalequalization-and-demultiplexing according to the fifth embodiment.

FIG. 22 illustrates data input to IDFT units 116 and 117 according tothe fifth embodiment.

FIG. 23 illustrates outputs of DFT units 213 and 214 according to thefifth embodiment.

FIG. 24 is a schematic block diagram illustrating a configuration of abase station device 502 according to a sixth embodiment of the presentinvention.

FIG. 25 illustrates spreading and multiplexing performed byspreading-and-multiplexing units 50-1 and 50-2 according to the sixthembodiment.

FIG. 26 is a schematic block diagram illustrating a configuration of aradio communication system according to a seventh embodiment of thepresent invention.

FIG. 27 illustrates example mapping of subcarriers according to theseventh embodiment.

FIG. 28 is a schematic block diagram illustrating a configuration of amobile station device A80 a according to the seventh embodiment.

FIG. 29 is a schematic block diagram illustrating a configuration of abase station device A70 according to the seventh embodiment.

FIG. 30 is a schematic block diagram illustrating a configuration of abase station device 71 according to an eighth embodiment of the presentinvention.

FIG. 31 is a schematic block diagram illustrating configurations ofmobile station devices 82 a and 82 b according to a ninth embodiment ofthe present invention.

FIG. 32 is a schematic block diagram illustrating a configuration of abase station device 72 according to the ninth embodiment.

FIG. 33 is a schematic block diagram illustrating a configuration of amobile station device 83 according to a tenth embodiment of the presentinvention.

FIG. 34 illustrates an operation performed by aspreading-and-multiplexing unit 300 according to the tenth embodiment.

FIG. 35 illustrates an EXIT chart used for a method of determining therate of overlapping subcarriers according to an eleventh embodiment ofthe present invention.

FIG. 36 illustrates an EXIT chart when the number of subcarriers ischanged according to the eleventh embodiment.

FIG. 37 is a flowchart illustrating an operation of spectrum-allocationdetermination according to a twelfth embodiment of the presentinvention.

FIG. 38A illustrates an example of spectrum allocation when transmissionis performed using subcarriers some of which are shared by usersaccording to a thirteenth embodiment of the present invention.

FIG. 38B illustrates an example of spectrum allocation when transmissionis performed using subcarriers some of which are shared by usersaccording to the thirteenth embodiment.

FIG. 39 schematically illustrates a case where transmission per frame isperformed according to a fourteenth embodiment of the present invention.

FIG. 40 is a schematic block diagram illustrating a configuration of atransmission device performing MIMO transmission using conventionalSC-ASA.

FIG. 41A schematically illustrates a radio communication systemperforming MIMO transmission using the conventional SC-ASA.

FIG. 41B illustrates a first example of subcarrier selection performedby the radio communication system performing MIMO transmission using theconventional SC-ASA.

FIG. 41C illustrates a second example of subcarrier selection performedby the radio communication system performing MIMO transmission using theconventional SC-ASA.

FIG. 42 is a schematic block diagram illustrating a configuration of areception device performing MIMO transmission using the conventionalSC-ASA.

FIG. 43 illustrates an example of subcarrier selection performed by theradio communication system performing MIMO transmission using theconventional SC-ASA.

FIG. 44A is a schematic block diagram illustrating a configuration of atransmission device when two transmission stations perform usermultiplexing using the conventional SC-ASA.

FIG. 44B is a schematic block diagram illustrating a configuration of areception device when two transmission stations perform usermultiplexing using the conventional SC-ASA.

FIG. 45 illustrates transmission-and-reception channels for conventionalMIMO transmission.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 encoder    -   2 modulator    -   3 S/P converter    -   4-1 and 4-2 DFT unit    -   5-1, 5-2, and 5-3 mapping unit    -   6-1 and 6-2 IDFT unit    -   7-1 and 7-2 GI inserter    -   8-1 and 8-2 P/S converter    -   9-1 and 9-2 D/A converter    -   10-1 and 10-2 RF unit    -   11 receiver    -   100, 101, 310, and 311 antenna    -   102, 103, 312, and 313 RF unit    -   104, 105, 314, and 315 A/D converter    -   106, 107, 316, and 317 CP remover    -   108, 109, 135, 136, 318, 319, and 212 S/P converter    -   110, 111, 116, 117, 137, 138, 139, 140, 215, 216, 320, and 321        DFT unit    -   112 and 113 channel estimator    -   114 and 200 canceller    -   115, 201-1, 201-2, and 300 signal equalizing-and-demultiplexing        unit    -   118 and 500 spatial-and-spectral demapping unit    -   301 spectral demapping unit    -   119, 120, 121, 122, 142, and 143 IDFT unit    -   123 and 124 P/S converter    -   125 and 126 demodulator    -   127 and 128 decoder    -   129, 130, and 205 repetition controller    -   131, 132, and 207 determining unit    -   133, 134, and 210 replica generator    -   141 spectral mapping unit    -   144 and 220 channel multiplier    -   145 and 221 channel reconfiguring unit    -   146 spectrum determining unit    -   147 interference power estimator    -   148 transmitter    -   500, 501, and 502 mobile station device    -   510, 511, 512, 513, and 514 base station device    -   A1, A200 a, and A200 b encoder    -   A2, A32-1, A32-2, A117, A201, and A230 interleaver    -   A3 and A202 modulator    -   A4, A34-1, A34-2, A203, and A232 S/P converter    -   A5, A24, A35-1, A35-2, A109, A120, A204, A224, 2A33 DFT unit    -   A6, A122, and A206 spectral mapping unit    -   A7, A123, and A207 IDFT unit    -   A8, A124, and A208 P/S converter    -   A9 pilot signal generator    -   A10 and A210 pilot multiplexer    -   A11 and A211 CP inserter    -   A12 and A212 D/A converter    -   A13, A39, A126, A213, and A241 radio unit    -   A14, A15, A100, A214, and A240 antenna    -   A16, A101, and A216 A/D converter    -   A17, A102, and A217 CP remover    -   A18, A103, and A218 pilot demultiplexer    -   A19, A104-1, A104-2, A219-1, and A219-2 channel estimator    -   A20, A127, and A220 spectrum-allocation determining unit    -   A21-1, A21-2, A221-1, and A221-2 channel-characteristic        demapping unit    -   A22-1, A22-2, A222-1, and A222-2 channel characteristic selector    -   A23, A108, A119, and A223 S/P converter    -   A25, A110, and A225 spectral demapping unit    -   A26-1 and A26-2 signal canceller    -   A27-1, A27-2, A112, A226, and A236 signal equalizer    -   A28-1, A28-2, A113, A227, and A237 demodulator    -   A29-1, A29-2, A114, A228, and A238 deinterleaver    -   A30-1, A30-2, A115, A229, and A239 decoder    -   A31-1, A31-2, and A116 repeated-number controller    -   A33-1, A33-2, A118, and A231 replica generator    -   A36-1, A36-2, A121, and A234 interference spectrum selector    -   A37-1, A37-2, and A125 determining unit    -   A38, A128, and A242 transmitter    -   A42 and A215 receiver    -   A50 demapping unit    -   A60 signal detector    -   A70, A71, and A72 base station device    -   A80 a, A80 b, A82 a, A82 b, and A83 mobile station device    -   A105-1 and A105-2 channel-characteristic demapping-and-selecting        unit    -   A106 user change controller    -   A107 and A235 interference signal canceller    -   A111 desired signal canceller    -   A300 spreading-and-multiplexing unit

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

A first embodiment explains a method of determining subcarriers used fortransmitting data from respective antennas based on channel conditionsfor respective subcarriers and for respective antennas. A radiocommunication system of the first embodiment includes multiple mobilestation devices and a base station device. The base station device is areception device of the first embodiment. The mobile station device is atransmission device of the first embodiment. The number of mobilestation devices simultaneously connected to the base station device istwo. The number of transmission antennas included in each mobile stationdevice is also two. Signals are transmitted from a total of fourtransmission antennas.

A transmission method used by the mobile station device is DFT-S-OFDM.The total number of subcarriers is 32. The number of subcarriers usedfor each antenna of each mobile station device is 16. The number ofreception antennas of the base station device is also two. Todemultiplex a signal received by the two antennas for each transmissionantenna, it is assumed in the first embodiment that any two of the totalof four transmission antennas are used for simultaneously transmittingsignals on one subcarrier.

FIG. 1 is a control flow illustrating a method of selecting subcarriersused for transmission of data according to the first embodiment. It isassumed for convenience that the two transmission antennas of a user 1are assigned the antenna numbers “1” and “2”, respectively, and that thetwo transmission antennas of a user 2 are assigned the antenna numbers“3” and “4”, respectively. Step S1 shown in FIG. 1 denotes an operationof generating two functions of f(a, b) and g(a, b). Each of thefunctions is an a×b matrix. a is the number of users×the number oftransmission antennas, which is 2×2=4 in the case of the firstembodiment. b is the number of subcarriers, which is 32 in the case ofthe first embodiment. As a value of the function f, channel capacityC_(m)(k) of each subcarrier to be transmitted from each transmissionantenna, which can be expressed as the following expression (1), or avalue corresponding to the channel capacity when calculation issimplified by, for example, omitting a constant term from the expression(1) so that the magnitude relationship does not change. m denotes thetransmission antenna number. k denotes the subcarrier number. N_(T) isthe number of transmission antennas. E_(s) denotes transmission energyfor one user. ξ_(m)(k) denotes a channel vector of the k-th subcarrierto be transmitted from the m-th transmission antenna. Σm(k) denotesinterference noise power of the k-th subcarrier to be transmitted fromthe m-th transmission antenna. Σ_(m)(k) can be expressed as anexpression (1′) where η(k) denotes an interference noise vector of eachreception antenna.

$\begin{matrix}{{C_{m}(k)} = {\log_{2}\left( {1 + {\frac{E_{S}}{N_{T}}{\xi_{m}^{H}(k)}{\xi_{m}(k)}\Sigma_{m}^{- 1}\;(k)}} \right)}} & (1) \\{{\Sigma_{m}(k)} = {E\left\lbrack {{{\xi_{m}(k)}^{H}{\eta(k)}}}^{2} \right\rbrack}} & \left( 1^{\prime} \right)\end{matrix}$

In the expression (1′), E[x] denotes an ensemble mean, and ∥x∥ denotes anorm of a vector x.

The expression (1) denotes channel capacity for each subcarrier to betransmitted from each transmission antenna at the time of SIMO (SingleInput Multi Output) transmission. This expression can be used as acriterion for selecting subcarriers to be used when all interferenceelements among signals transmitted from the respective transmissionantennas can be cancelled by an operation on a receiving side that willbe explained later. Such a case is called a complete convergence stateof reception processing, and can achieve reception characteristics atthe time of SIMO transmission. Accordingly, transmission subcarriers areselected independently for each transmission antenna based on theexpression (1), thereby achieving a diversity effect that is moreflexible and higher than that achieved by the conventional selectionmethod.

The function g initializes all values to 0. By performing the operationshown in the flowchart of FIG. 1, the function g becomes a functionindicative of presence or absence of signal transmission for acombination of the input antenna number and the subcarrier number. Forexample, if g(2, 5)=1, then a signal is transmitted on the fifthsubcarrier from the second antenna. Step S2 is a step of extracting theelement number of a matrix having the maximum value of the function f.In other words, x and y of a matrix having x rows and y columns to whichelements for the maximum value are assigned are calculated. Then, stepS4 is a step of determining whether or not the number of transmissionantennas already assigned to the y column of the function g is 1 orless. In other words, it is a step of determining whether or not thenumber of transmission antennas from which signals are transmitted onthe y-th subcarrier is 1 or less. This determination is performed byadding each element of the y column and thereby calculating the numberof transmission antennas from which signals are transmitted on the y-thsubcarrier.

The condition of step S4 that the number is 1 or less depends on theaforementioned assumption that the maximum number of antennas assignedto the same subcarrier is set to two. If it is determined in step S4that the number is 1 or less, and if assignment can be still performed(S4: YΞS), then g(x, y)=1 in step S5 and a fact that assignment has beendone is reflected in the function g. In step S6, the number of thefunction g having the value of 1 is counted and compared to 64. Sincethis value is incremented by 1, the time when the value becomes 64indicates completion of all assignments. It is noted that 64=the numberof subcarriers used for each antenna (16)×the total number of antennasof mobile station devices simultaneously connected to the base stationdevices (4).

If two antennas have already been assigned in step S4 and if it isdetermined in step S6 that assignment is still required, a value of thefunction f with respect to elements x and y currently selected in stepS7 is set to −100. The value of −100 has no significant meaning andindicates that the value is changed to a small value so that the sameelements are not selected again in step S2.

A result of the selection performed in this manner is shown in FIG. 2.In FIG. 2, the vertical axis denotes the antenna number for each mobilestation, and the horizontal axis denotes the subcarrier number.Subcarriers each surrounded by a square indicate subcarriers to be usedfor transmission of signals. In the case of FIG. 2, the 30th and 32ndsubcarriers correspond to the case of single-user MIMO in which onemobile station device multiplexes signals. In other words, thesubcarrier 30 is used by the antennas 1 and 2 of the user 1. Thesubcarrier 32 is used by the antennas 1 and 2 of the user 2. The 1st,2nd, 3rd, and 31st subcarriers correspond to the case of multi-user MIMOin which multiple mobile station devices share subcarriers to be usedwith one another and multiplex signals. In other words, for example,subcarrier 1 is used by the antenna 1 of the user 1 and the antenna 2 ofthe user 2. Thus, subcarriers to be independently used for each antennaare selected based on only the channel conditions, thereby enablingtransmission of data in a good condition.

Although an antenna for transmitting a subcarrier is determined herebased on only channel conditions without setting likelihoods to allantennas, if there is a large difference in channel conditions betweenthe first and second mobile station devices, one of the mobile stationdevices cannot always select subcarriers having good channel conditions.To cope with this situation, the function f is provided for each mobilestation device so that each mobile station device sequentially selects asubcarrier.

Although the result of the calculation by the expression (1) is used asa value of the function f in the above case, alternatively, a channelcondition (channel gain), SINR (Signal to Interference Noise Ratio)(this interference means unknown interference elements received from anadjacent cell or the like), or the like for each transmission antennaand for each subcarrier may be substituted as a value of the function f.However, two channels are present for one transmission antenna in thefirst embodiment (since the base station device has two receptionantennas). For this reason, channel conditions or SINRs monitored by thetwo reception antennas are added or averaged for each subcarrier to beused as each element of the function f. Even when a simple criterionsuch as an average of SINR for each reception antenna is used, asubcarrier to be transmitted can be selected independently for eachtransmission antenna similarly to the case of using the expression (1).

FIG. 3 is a schematic block diagram illustrating a configuration of amobile station device 500 for performing transmission using thesubcarriers independently selected for each transmission antenna of eachmobile station device based on the control flow shown in FIG. 1. Asshown in FIG. 3, a reference numeral 11 denotes a receiver thatreceives, from the base station device through an antenna, mappinginformation indicative of a subcarrier to be used for transmission of asignal with respect to each transmission antenna. A reference numeral 1denotes an encoder that performs error correction coding on transmissiondata. A reference numeral 2 denotes a modulator (hereinafter called “afirst modulator”) that performs modulation, such as BPSK (Binary PhaseShift Keying) on an output of the encoder 1. A reference numeral 3denotes an S/P (Serial/Parallel) converter that converts the modulatedsignal output from the modulator 2, which is serial input data, intoparallel data corresponding to MIMO. The receiver 11 may use the firstor second antennas.

Since it is assumed that two transmission antennas are included in thefollowing circuit, there are two systems (x-1 and x-2). A referencenumeral 4 denotes a DFT unit that performs DFT (Discrete FourierTransform) on the modulated signals received from the S/P converter 3for frequency spreading. Reference numerals 5-1 and 5-2 denote mappingunits that allocate the signals subjected to the frequency spreadingperformed by the DFT units 4-1 and 4-2 onto subcarriers to be used basedon the mapping information received by the receiver 11 from the basestation device, respectively. Subcarriers are specified independentlyfor the mapping units 5-1 and 5-2, which are subcarriers calculated bythe function g. “0” is input to subcarriers onto which no data ismapped.

Reference numerals 6-1 and 6-2 are IDFT units that perform IDFT (InverseDiscrete Fourier Transform) on the signals mapped onto subcarriers bythe mapping units 5-1 and 5-2, respectively. Reference numerals 7-1 and7-2 are GI inserters that insert guard intervals into the outputs of theIDFT units 6-1 and 6-2, respectively. The GI inserters 7-1 and 7-2 copythe last part of the input data to a GI section, which is called acyclic prefix. The reason that a cyclic prefix is used is explainedhere. Waves to be subjected to DFT in the DFT section are required tohave a period that is an integral multiple of one period of a periodicalfunction. For this reason, if delayed-wave elements are present inmultipath channels, the functional periodicity of the delayed-waveelements of the received signal collapses on the receiving side.Consequently, the received signal cannot be demultiplexed intosubcarriers by DFT, and therefore subcarriers cannot be independentlyprocessed.

On the other hand, if a cyclic prefix corresponding to the maximum delaytime of the channel is preliminarily inserted on the transmitting side,the cyclic prefix is removed on the receiving side so that thefunctional periodicity with respect to the delayed elements can bemaintained. Consequently, each subcarrier can be independentlyprocessed. In other words, even if each subcarrier is allocated to anarbitral frequency, the subcarrier can be reproduced on the receivingside.

Reference numerals 8-1 and 8-2 are P/S (Parallel/Serial) converters thatconvert the outputs of the GI inserters 7-1 and 7-2, which are paralleldata, into serial data, respectively. Reference numerals 9-1 and 9-2 areD/A (Digital/Analog) converters that convert the outputs of the P/Sconverters 8-1 and 8-2, which are digital data, into analog data.Reference numerals 10-1 and 10-2 are RF (Radio Frequency) units thatconvert data into a frequency band to be transmitted. The first andsecond independent antennas are connected to the RF units 10-1 and 10-2,respectively. Although one encoder 1 is used for multiple transmittedsignals in the first embodiment, different encoders may be used forrespective signals transmitted from the transmission antennas.

As shown in FIG. 3, the mobile station device 500 includes the encoder1, the converter 2, the S/P converter 3, the DFT units 4-1 and 4-2, themapping units 5-1 and 5-2, the IDFT units 6-1 and 6-2, the GI inserters7-1 and 7-2, the P/S converters 8-1 and 8-2, the D/A converters 9-1 and9-2, the RF units 10-1 and 10-2, and the receiver 11.

According to the configuration, transmission of data is enabledaccording to allocation of subcarriers determined for each antenna basedon the flow shown in FIG. 1.

Hereinafter, operations of the mapping units 5-1 and 5-2 are explainedto explain the state of mapping onto subcarriers with reference to theuser 1 shown in FIG. 2. It is assumed that subcarriers used by the “user1, antenna 1” shown in FIG. 2 are 16 subcarriers (corresponding to thesubcarrier numbers 1, 3, 5, 8, 10, 11, 14, 17, 20, 22, 24, 25, 28, 30,31, and 32). It is assumed that subcarriers used by the “user 1, antenna2” are 16 subcarriers (corresponding to the subcarrier numbers 2, 4, 5,6, 7, 8, 11, 15, 17, 19, 20, 22, 23, 26, 30, and 31). The user 1indicates the mobile station device 500 corresponding to the mobilestation number of 1. The antenna 1 indicates the antenna correspondingto the antenna number of 1. The similar applies to the user 2 and theantenna 2.

FIG. 4 illustrates operations of the mapping units 5-1 and 5-2.Information concerning subcarriers to be used (mapping information) foreach antenna is input from the receiver 11 to the mapping units 5-1 and5-2. As shown in FIG. 4, the left side of the mapping units 5-1 and 5-2is the input side (there are 16 inputs since the number of subcarriersto be used is assumed to be 16). The right side of the mapping units 5-1and 5-2 is the output side (there are 32 outputs since selection is madefrom 32 subcarriers). Output signals to which no input signal isconnected is a null signal. In the example of the mapping unit 5-1 shownin FIG. 4, the first and second input signals are allocated to the firstand third subcarriers, respectively. Since no input signal is allocatedto the second subcarrier, 0 is output from the second subcarrier.Although the mapping units 5-1 and 5-2 are configured in the case ofFIG. 4 such that inputs and outputs are connected based on selection,the mapping units 5-1 and 5-2 may be configured such that input signalsare input to memory, and are then read out on the output side based onthe mapping information.

FIG. 5 is a schematic block diagram illustrating a configuration of amobile station device 501 that is another example of a configuration ofthe mobile station device 500. Like reference numerals denote blockshaving the same functions in FIGS. 3 and 5. Different from FIG. 3, theDFT unit 4-2 is not included, and instead only the DFT unit 4-1 isincluded in FIG. 5. The mapping units 5-1 and 5-2 are not included, andonly the mapping unit 5-3 is included in FIG. 5. This is because themapping unit 5-3 of the mobile station device 501 simultaneously mapstwo symbols of a spectrum output from the DFT unit 4-1. Transmittedsignals to be transmitted from multiple transmission antennas areconfigured in this manner. The DFT unit 4-1 shown in FIG. 5 may have theinput-output size which is double that of the DFT unit 4-1 shown in FIG.3.

Although subcarriers to be used are determined based on the control flowshown in FIG. 1 in the first embodiment, the determination ofsubcarriers may be performed for each frame of a target radiocommunication system. Thus, subcarriers are selected for each frame,thereby enabling selection of subcarriers corresponding to a timevariation of channel conditions, and therefore further enhancing thefrequency utilization efficiency.

Explanations of the base station device will be given in the followingembodiments.

According to the first embodiment, transmission subcarriers are selectedindependently for each transmission antenna as in the flowchart shown inFIG. 1, thereby enabling selection of subcarriers having the bestconditions among transmittable channels, and therefore achieving higherfrequency utilization efficiency for each mobile station device and forthe entire system.

Second Embodiment

The second embodiment explains a configuration of a reception device towhich SC/MMSE (Soft Canceller/MMSE)-technique is applied, in which withrespect to single-user-MIMO-and-multi-user-MIMO-mixed signals subjectedto the spatial-and-spectral mapping of the present invention, replicasof received signals are generated based on the reliability ofdemodulated data, unnecessary interference (replicas) are subtractedfrom the received signals, and then a series of operations, such asequalization and demodulation, is repeated, thereby gradually increasingthe reliability of the demodulated data.

Similar to the first embodiment, it is assumed in the second embodimentthat the number of mobile station devices simultaneously connected tothe base station device is two. The number of transmission antennasincluded in each mobile station device is also two. Signals aretransmitted from a total of four transmission antennas. A transmissionmethod used by the mobile station device is DFT-S-OFDM. The total numberof subcarriers is 32. The number of subcarriers used for each antenna ofeach mobile station device is 16. The number of reception antennas ofthe base station device is also two. To demultiplex a signal received bythe two antennas for each transmission antenna, it is assumed in thesecond embodiment that any two of the total of four transmissionantennas are used for simultaneously transmitting signals on onesubcarrier.

FIG. 6 is a schematic block diagram illustrating a configuration of abase station device 510 that is a reception device according to thesecond embodiment. As shown in FIG. 6, the reception device according tothe second embodiment includes: antennas 100 and 101; RF units 102 and103; A/D converters 104 and 105; CP removers 106 and 107; S/P converters108, 109, 135, and 136; DFT units 110, 111, 116, 117, 137, 138, 139, and140; channel estimators 112 and 113; a canceller 114; signalequalizing-and-demultiplexing unit 115; a spatial-and-spectral demappingunit 118; IDFT units 119, 120, 121, 122, 142, and 143; P/S converters123 and 124; demodulators 125 and 126; decoders 127 and 128; repetitioncontrollers 129 and 130; determining units 131 and 132; replicagenerators 133 and 134; a spatial-and-spectral mapping unit 141; achannel multiplier 144; a channel reconfiguring unit 145; a spectrumdetermining unit 146; an interference-power measuring unit 147; and atransmitter 148.

Regarding the base station device 510 shown in FIG. 6, signals receivedby the antennas 100 and 101 pass through the CP removers 106, 107, andthe like, and then are converted into frequency-domain signals by DFTperformed by the DFT units 110 and 111. Then, the frequency-domainsignals are input to the canceller 114. The canceller 114 subtractsreplicas of the received signals generated based on the reliability ofdemodulated data from the frequency-domain signals that are the receivedsignals.

If a perfect replica (transmitted signal) is generated, an output of thecanceller 114 includes only noise elements. This calculation can beexpressed as an expression (2) where R denotes a reception-data vectorreceived by the two antennas, Ξ denotes a virtual channel matrix (amatrix generated by the channel reconfiguring unit 221 mapping, based onthe mapping information, channel variations estimated by the channelestimators 112 and 113), and S′ denotes a replica of a pseudotransmission-data vector (generated by replica generators 133 and 134 tothe spatial-and-spectral mapping unit 141 as will be explained later)generated by gathering signals to be transmitted from all thetransmission antennas into one vector.Q=R−ΞS′  (2)

In the above expression, Q denotes a vector indicative of an output ofthe canceller 114 (residual after cancelling) at the time of thesecond-or-more repeated operation. R, Ξ, and S′ are expressed as thefollowing expressions (3) to (5).

$\begin{matrix}{R = \begin{bmatrix}{\;{R_{\; 1}\;(1)}} \\{\;{R_{\; 1}\;(2)}} \\{\;{R_{\; 1}\;(3)}} \\{\;{R_{\; 1}\;(4)}} \\{\;{R_{\; 2}\;(1)}} \\{\;{R_{\; 2}\;(2)}} \\{\;{R_{\; 2}\;(3)}} \\{\;{R_{\; 2}\;(4)}}\end{bmatrix}} & (3) \\{\Xi = \begin{bmatrix}{\;{\Xi_{\; 13}\;(1)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 14}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 12}\;(2)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 13}\;(2)}} & 0 & 0 \\0 & 0 & {\Xi_{\; 11}\;(3)} & 0 & 0 & 0 & {\Xi_{\; 14}\;(3)} & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 11}\;(4)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 12}\;(4)}} \\{\;{\Xi_{\; 23}\;(1)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 24}\;(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 22}\;(2)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 23}\;(2)}} & 0 & 0 \\0 & 0 & {\Xi_{\; 21}\;(3)} & 0 & 0 & 0 & {\Xi_{\; 24}\;(3)} & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 21}\;(4)}} & 0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 22}\;(4)}}\end{bmatrix}} & (4) \\{S^{\prime} = \begin{bmatrix}{\;{S_{\; 3}^{\;\prime}\;(1)}} \\{\;{S_{\; 2}^{\;\prime}\;(2)}} \\{S_{\; 1}^{\;\prime}\;(3)} \\{\;{S_{\; 1}^{\;\prime}\;(4)}} \\{\;{S_{\; 4}^{\;\prime}\;(1)}} \\{\;{S_{\; 3}^{\;\prime}\;(2)}} \\{S_{\; 4}^{\;\prime}\;(3)} \\{\;{S_{\; 2}^{\;\prime}\;(4)}}\end{bmatrix}} & (5)\end{matrix}$

The reason that all replicas (ΞS′) including desired signals to beextracted are cancelled is that the signal equalizing-and-demultiplexingunit 115 that will be explained later performs an inverse matrixcalculation, and therefore the inverse matrix calculation has to beperformed a number of times corresponding to the number of desiredsignals included in a block if cancelling and equalization are repeatedwithout cancelling the desired signals. On the other hand, if theresidual Q after cancelling all the replicas is input, the residual canbe equally treated in the block, and therefore all weights can becalculated with one inverse calculation for the block. For this reason,the replica is independently input and reconfigured to decrease theamount of the inverse calculation. However, a replica of the receivedsignal cannot be generated for the first operation. In this case, thereception-data vector (R) passes through the canceller 114 as it is.

The signal output from the canceller 114 is input to the signalequalizing-and-demultiplexing unit 115, and then subjected toequalization using frequency-domain signals. If the repeated operationis performed, the signal equalizing-and-demultiplexing unit 115 performsequalization on an output (Q) of the canceller 114 to which a replica ofthe received signal for each transmission-data vector is added. Thetransmission-data vector targeted for the equalization performed by thesignal equalizing-and-demultiplexing unit 115 when thespatial-and-spectral mapping of the present invention is performed isnot a transmission data stream in the case of normal single-user MIMO ormulti-user MIMO, i.e., transmission data for each transmission antennaor for each mobile station device, but is a data stream generated bydemultiplexing two signals actually multiplexed into one spectrumirrespective of transmission sources and then gathering thosedemultiplexed signals with respect to the entire spectrum.

For example, it is assumed that spatial-and-spectral mapping as shown inFIG. 7 is performed. Transmission-data vectors targeted for equalizationperformed by the signal equalizing-and-demultiplexing unit 115 of thebase station device 510 with respect to transmitted signals in this caseare two signal streams, i.e., a signal stream expressed by shaded blocksB1, B2, B3, and B4 and a signal steam expressed by white blocks B5, B6,B7, and B8. Thus, the signal equalizing-and-demultiplexing unit 115 ofthe second embodiment virtually regards the two signal streams includingthe mixed signals transmitted from the respective antennas of multipleusers as shown in FIG. 7 as one signal transmitted from one antenna, andperforms equalization independently for each signal stream. The user 1indicates the mobile station device 510 corresponding to the mobilestation number 1. The antenna 1 indicates the antenna corresponding tothe antenna number 1. The similar applies to the user 2 and the antenna2.

Hereinafter, the two virtual signal streams are called a pseudotransmission-data vector 1 (the signal stream expressed by the shadedblocks B1 to B4 shown in FIG. 7 corresponding to an upper half of S′)and a pseudo transmission-data vector 2 (the signal stream expressed bythe white blocks B5 to B8 shown in FIG. 7 corresponding to an lower halfof S′). Since a replica of a received signal is not generated for thefirst operation, a signal passes through the canceller 200 without beingsubjected to any subtraction, and then is subjected to equalization. Asexplained above, the equalization of the second embodiment is performedon each of the pseudo transmission vectors 1 and 2 (the two signalstreams distinguishably expressed by the shaded blocks and the whiteblocks shown in FIG. 7). Therefore, calculation is performed using thereception-data vector shown in the expression (3), a virtual channelmatrix shown in the expression (4), and channel matrices Ξ_(T1) andΞ_(T2) with respect to the pseudo transmission-data vectors 1 and 2.

Ξ_(T1) and Ξ_(T2) are virtual channel matrices generated under theassumption that the respective transmission-data vectors are regarded asa signal transmitted from one antenna, which are used for equalizing thepseudo transmission-data vectors 1 and 2, respectively. Since Ξ_(T1) andΞ_(T2) are a part of the virtual channel matrix Ξ, these matrices arehereinafter called “virtual subchannel matrices”. These virtualsubchannel matrices are obtained by channel estimation values for eachcombination of transmission-and-reception antennas, which are obtainedby the channel estimators 112 and 113, being mapped based on thespectral mapping information. In the second embodiment, these virtualsubchannel matrices are generated by the channel reconfiguring unit 145.

$\begin{matrix}{\Xi_{T\; 1} = \begin{bmatrix}{\;\Xi_{\; 13}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 12}} & 0 & 0 \\0 & 0 & \Xi_{\; 11} & 0 \\0 & 0 & 0 & {\mspace{11mu}\Xi_{\; 11}} \\{\;\Xi_{\; 23}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 22}} & 0 & 0 \\0 & 0 & \Xi_{\; 21} & 0 \\0 & 0 & 0 & {\mspace{11mu}\Xi_{\; 21}}\end{bmatrix}} & (6) \\{\Xi_{T\; 2} = \begin{bmatrix}{\;\Xi_{\; 14}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 13}} & 0 & 0 \\0 & 0 & \Xi_{\; 14} & 0 \\0 & 0 & 0 & {\mspace{11mu}\Xi_{\; 12}} \\{\;\Xi_{\; 24}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 23}} & 0 & 0 \\0 & 0 & \Xi_{\; 24} & 0 \\0 & 0 & 0 & {\mspace{11mu}\Xi_{\; 22}}\end{bmatrix}} & (7)\end{matrix}$

Hereinafter, an operation of the channel reconfiguring unit 145 isexplained. The channel reconfiguring unit 145 receives channelestimation information from each reception antenna. The information tobe received is a channel response for each subcarrier with respect toeach transmission-and-reception antenna. Since it is assumed in thesecond embodiment that the number of transmission antennas required tobe simultaneously processed is 4 (the number of users 2×the number ofantennas 2), the number of antennas is 2, and the number of subcarriersis 4, a total of 32 frequency responses are received. Channelinformation Ξ_(r1) received from the channel estimator 112 connected tothe antenna 100 can be expressed as an expression (8). Channelinformation Ξ_(r2) received from the channel estimator 113 connected tothe antenna 101 can be expressed as an expression (9) (wheretransmission antennas of the user 1 are denoted as transmission antennas1 and 2, and transmission antennas of the user 2 are denoted astransmission antennas 3 and 4).

$\begin{matrix}{\Xi_{r\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & {\Xi_{11}(2)} & {\Xi_{11}(3)} & {\Xi_{11}(4)} \\{\Xi_{12}(1)} & {\Xi_{12}(2)} & {\Xi_{12}(3)} & {\Xi_{12}(4)} \\{\Xi_{13}(1)} & {\Xi_{13}(2)} & {\Xi_{13}(3)} & {\Xi_{13}(4)} \\{\Xi_{14}(1)} & {\Xi_{14}(2)} & {\Xi_{14}(3)} & {\Xi_{14}(4)}\end{bmatrix}} & (8) \\{\Xi_{r\; 2} = \begin{bmatrix}{\Xi_{21}(1)} & {\Xi_{21}(2)} & {\Xi_{21}(3)} & {\Xi_{21}(4)} \\{\Xi_{22}(1)} & {\Xi_{22}(2)} & {\Xi_{22}(3)} & {\Xi_{22}(4)} \\{\Xi_{23}(1)} & {\Xi_{23}(2)} & {\Xi_{23}(3)} & {\Xi_{23}(4)} \\{\Xi_{24}(1)} & {\Xi_{24}(2)} & {\Xi_{24}(3)} & {\Xi_{24}(4)}\end{bmatrix}} & (9)\end{matrix}$

The channel reconfiguring unit 145 generates the virtual channel matrixΞ and the virtual subchannel matrices Ξ_(T1) and Ξ_(T2). Hereinafter, amethod of generating the virtual channel matrix is explained first. Amasking vector MV by which the expressions (8) and (9) are multiplied isgenerated based on mapping information, i.e., usage of subcarriers foreach antenna shown in FIG. 8. The masking vector MV is a vector in which1 is set to a portion to be used, and 0 is set to a portion not to beused. The masking vector MV corresponding to the case of FIG. 8 can beexpressed as an expression (10).

$\begin{matrix}{{MV} = \begin{bmatrix}0 & 0 & 1 & 1 \\0 & 1 & 0 & 1 \\1 & 1 & 0 & 0 \\1 & 0 & 1 & 0\end{bmatrix}} & (10)\end{matrix}$

If “. *” denotes products of respective elements of two matrices,

$\begin{matrix}{{\Xi_{r\; 1} \cdot^{*}{MV}} = \begin{bmatrix}0 & 0 & {\Xi_{11}(3)} & {\Xi_{11}(4)} \\0 & {\Xi_{12}(2)} & 0 & {\Xi_{12}(4)} \\{\Xi_{13}(1)} & {\Xi_{13}(2)} & 0 & 0 \\{\Xi_{14}(1)} & 0 & {\Xi_{14}(3)} & 0\end{bmatrix}} & (11) \\{{\Xi_{r\; 2} \cdot^{*}{MV}} = \begin{bmatrix}0 & 0 & {\Xi_{21}(3)} & {\Xi_{21}(4)} \\0 & {\Xi_{22}(2)} & 0 & {\Xi_{22}(4)} \\{\Xi_{23}(1)} & {\Xi_{23}(2)} & 0 & 0 \\{\Xi_{24}(1)} & 0 & {\Xi_{24}(3)} & 0\end{bmatrix}} & (12)\end{matrix}$

It is assumed that D0U(A) denotes a calculation of removing 0 elementsfrom a matrix A, and then upwardly shifting elements. If the calculationof D0U(A) is performed on the expressions (11) and (12),

$\begin{matrix}{{D\; 0\;{U\left( {\Xi_{r\; 1} \cdot^{*}{MV}} \right)}} = \begin{bmatrix}{\Xi_{13}(1)} & {\Xi_{12}(2)} & {\Xi_{11}(3)} & {\Xi_{11}(4)} \\{\Xi_{14}(1)} & {\Xi_{13}(2)} & {\Xi_{14}(3)} & {\Xi_{12}(4)}\end{bmatrix}} & (13) \\{{D\; 0\;{U\left( {\Xi_{r\; 2} \cdot^{*}{MV}} \right)}} = \begin{bmatrix}{\Xi_{23}(1)} & {\Xi_{22}(2)} & {\Xi_{21}(3)} & {\Xi_{21}(4)} \\{\Xi_{24}(1)} & {\Xi_{23}(2)} & {\Xi_{24}(3)} & {\Xi_{22}(4)}\end{bmatrix}} & (14)\end{matrix}$

The virtual channel matrix Ξ can be calculated by diagonalizing a 4×4square matrix using each column vector shown in the expressions (13) and(14) (an example where one row of the expression (13) is diagonalized isshown as a matrix (15)), by connecting square matrices generated fromthe same expression in the column direction to generate a 4×8 squarematrix (an example where diagonalized matrices generated from theexpression (13) are connected is shown as an expression (16)), and byconnecting the 4×8 square matrix in the row direction.

$\begin{matrix}\begin{bmatrix}{\;{\Xi_{\; 13}(1)}} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 12}(2)}} & 0 & 0 \\0 & 0 & {\Xi_{\; 11}(3)} & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 11}(4)}}\end{bmatrix} & (15) \\\begin{bmatrix}{\;{\Xi_{\; 13}(1)}} & 0 & 0 & 0 & {\Xi_{\; 14}(1)} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 12}(2)}} & 0 & 0 & 0 & {\Xi_{\; 13}(2)} & 0 & 0 \\0 & 0 & {\Xi_{\; 11}(3)} & 0 & 0 & 0 & {\Xi_{\; 14}(3)} & 0 \\0 & 0 & 0 & {\mspace{11mu}{\Xi_{\; 11}(4)}} & 0 & 0 & 0 & {\Xi_{\; 12}(4)}\end{bmatrix} & (16) \\{\Xi = \begin{bmatrix}{\;{\Xi_{\; 13}(1)}} & 0 & 0 & 0 & {\Xi_{\; 14}(1)} & 0 & 0 & 0 \\0 & {\mspace{11mu}{\Xi_{\; 12}(2)}} & 0 & 0 & 0 & {\Xi_{\; 13}(2)} & 0 & 0 \\0 & 0 & {\Xi_{\; 11}(3)} & 0 & 0 & 0 & {\Xi_{\; 14}(3)} & 0 \\0 & 0 & 0 & {\Xi_{\; 11}(4)} & 0 & 0 & 0 & {\Xi_{\; 12}(4)} \\{\Xi_{\; 23}(1)} & 0 & 0 & 0 & {\Xi_{\; 24}(1)} & 0 & 0 & 0 \\0 & {\Xi_{\; 22}(2)} & 0 & 0 & 0 & {\Xi_{\; 23}(2)} & 0 & 0 \\0 & 0 & {\Xi_{\; 21}(3)} & 0 & 0 & 0 & {\Xi_{\; 24}(3)} & 0 \\0 & 0 & 0 & {\Xi_{\; 21}(4)} & 0 & 0 & 0 & {\Xi_{\; 22}(4)}\end{bmatrix}} & (17)\end{matrix}$

The 8×4 matrix that is the left half of the virtual channel matrix Ξ andthe 8×4 matrix that is the right half thereof are virtual subchannelmatrices.

$\begin{matrix}{\Xi_{T\; 1} = \begin{bmatrix}{\;\Xi_{\; 13}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 12}} & 0 & 0 \\0 & 0 & \Xi_{\; 11} & 0 \\0 & 0 & 0 & \Xi_{\; 11} \\\Xi_{\; 23} & 0 & 0 & 0 \\0 & \Xi_{\; 22} & 0 & 0 \\0 & 0 & \Xi_{\; 21} & 0 \\0 & 0 & 0 & \Xi_{\; 21}\end{bmatrix}} & (18) \\{\Xi_{T\; 2} = \begin{bmatrix}{\;\Xi_{\; 14}} & 0 & 0 & 0 \\0 & {\mspace{11mu}\Xi_{\; 13}} & 0 & 0 \\0 & 0 & \Xi_{\; 14} & 0 \\0 & 0 & 0 & \Xi_{\; 12} \\\Xi_{\; 24} & 0 & 0 & 0 \\0 & \Xi_{\; 23} & 0 & 0 \\0 & 0 & \Xi_{\; 24} & 0 \\0 & 0 & 0 & \Xi_{\; 22}\end{bmatrix}} & (19)\end{matrix}$

Although the case where a matrix is sequentially transformed to generatethe virtual channel matrix is shown here, the virtual channel matrix Ξmay be generated by storing Ξ_(r1) and Ξ_(r2) in memory and changing theorder of reading memory according to mapping information.

At the time of the repeated operations, equalization is performedinstead of using the reception-data vector shown in the expression (3),using the residual (Q) after the cancelling shown in the expression (2),and the signals, which are reconverted by IDFT units 142 and 143 intotime domain signals for each pseudo transmission-data vector after theDFT units 137 to 140 convert time-domain replicas into frequency-domainreplicas and the spatial-and-spectral mapping unit 141 performs mapping.In this case, replicas of the pseudo transmission-data vectors 1 and 2to be input to the IDFT units 142 and 143 can be expressed as thefollowing expressions. In the following expressions, S′_(T1) denotes thepseudo transmission-data vector 1 (shaded signal stream B1 to B4 shownin FIG. 7), S′_(T2) denotes the pseudo transmission-data vector 2 (whitesignal stream B5 to B8 shown in FIG. 7), respectively. The base stationdevice 510 of the second embodiment reconfigures received signals foreach pseudo transmission-data vector using these replicas, and therebyperforms MMSE equalization using an expression (22).

$\begin{matrix}{S_{T\; 1}^{\prime} = \begin{bmatrix}{\;{S_{\; 3}^{\;\prime}\;(1)}} \\{\;{S_{\; 2}^{\;\prime}\;(2)}} \\{\;{S_{\; 1}^{\;\prime}\;(3)}} \\{S_{\; 1}^{\;\prime}\;(4)}\end{bmatrix}} & (20) \\{S_{T\; 2}^{\prime} = \begin{bmatrix}{\;{S_{\; 4}^{\;\prime}\;(1)}} \\{\;{S_{\; 3}^{\;\prime}\;(2)}} \\{\;{S_{\; 4}^{\;\prime}\;(3)}} \\{S_{\; 2}^{\;\prime}\;(4)}\end{bmatrix}} & (21) \\{z_{Tn} = {\left( {1 + {\gamma_{Tn}\delta_{Tn}}} \right)^{- 1}\left\lbrack {{\gamma_{Tn}s_{Tn}^{\prime}} + {F^{H}\Psi_{Tn}Q}} \right\rbrack}} & (22)\end{matrix}$

In the above expressions, γ_(Tn) and δ_(Tn) denote real numbers usedwhen tap coefficients are calculated. Similarly, Ψ_(Tn) denotes acomplex square matrix having a size of the DFT block length, which areused when tap coefficients are calculated. z_(Tn) denotes a signal foreach pseudo transmission-data vector, which is output from the signalequalizing-and-demultiplexing unit 115. n of the suffix Tn correspondsto the number of the pseudo transmission-data vector, which is 1 or 2 inthe second embodiment.

Thus, the mixed signals to be transmitted from multiple transmissionantennas are regarded as pseudo transmission data, thereby enablingequalization using the expression (22) even when thespatial-and-spectral mapping of the present invention is performed. Inthis case, signals equalized in the time domain are output from thesignal equalizing-and-demultiplexing unit 115 for each pseudotransmission data.

The signals equalized for each pseudo transmission data are input to theDFT units 116 and 117, converted into frequency-domain signals, and theninput to spatial-and-spectral demapping unit 118. In this case, theequalized pseudo transmission-data vector 1 (shaded signal stream B1 toB4 shown in FIG. 7) and the equalized pseudo transmission-data vector 2(white signal stream B5 to B8 shown in FIG. 7) are input to the DFTunits 116 and 117, respectively. Based on the spectral mappinginformation, the spatial-and-spectral demapping unit 118 performsdemapping to group signals transmitted from each transmission antenna ofeach user. Since signals are transmitted from the two users using thetotal number of four transmission antennas, the spatial-and-spectraldemapping unit 118 groups signals into four signal streams.

Then, the IDFT units 119 to 122 convert the respective signal streamsdemapped in the spatial-and-spectral directions into time-domainsignals. According to the configuration, multiple signal streamssubjected to the spatial-and-spectral mapping of the present inventioncan be grouped into signal streams transmitted from the respectivetransmission antennas and then be subjected to IDFT. Then, the signalstreams subjected to the IDFT are converted by the P/S converters 123and 124 into serial signals for each user, and then subjected todemodulation and decoding. In this case, the operations up to oneperformed by the P/S converters 123 and 124 are performed in units ofOFDM symbols. The following operations, especially decoding, isperformed in units by which error correction coding is performed(usually, in units of packets or frames).

The decoders 127 and 128 calculate LLRs (Log Likelihood Ratios)indicative of the reliability of the reception data subjected to errorcorrection. The repetition controllers 129 and 130 receiving the LLRsdetermine whether or not the repeated operations have been performed apredetermined number of times. If the repeated operations have beenperformed the predetermined number of times, the repetition controllers129 and 130 output the LLRs to the determining units 131 and 132,respectively. If the repeated operations have not yet been performed thepredetermined number of times, the repetition controllers 129 and 130output the LLRs to the replica generators 133 and 134, and then theroutine returns to the operation of generating replicas of the receivedsignals. If it is assumed that a CRC (Cyclic Redundancy Check) code isused, the repetition controllers 129 and 130 may be configured toperform CRC check of the reception data, and to end the repeatedoperations if no error is detected.

The replica generators 133 and 134 generate signal replicas (replicas oftransmitted signals) corresponding to the LLRs of the respective bits.The generated replicas pass through the S/P converters 135 and 136, andthen converted by the DFT units 137 to 140 into frequency-domainreplicas of the signals transmitted from the respective transmissionantennas. Although it has been explained above that the operations afterthe demodulation are performed in units of packets or frames, theoperations from the DFT units 137 to 140 are performed in units of OFDMsymbols again.

Similar to the mapping on the transmitting side, thespatial-and-spectral mapping unit 141 performs mapping of the presentinvention on the frequency-domain replicas generated in this mannerbased on mapping information received from the spectrum determining unit146. Then, the replicas (S′) subjected to the spatial-and-spectralmapping are input to the signal equalizing-and-demultiplexing unit 115and the channel multiplier 144, respectively. The signalequalizing-and-demultiplexing unit 115 receiving the replicas (S′) afterthe spatial-and-spectral mapping reconfigures received signalscorresponding to the pseudo transmission-data vectors 1 and 2 usingthese replicas, and uses the reconfigured received signals forequalization of the respective pseudo transmission-data vectors. Togenerate replicas of received signals to be subtracted from receivedsignals by the canceller 114, the channel multiplier 144 multiples thereplicas after the spatial-and-spectral mapping by the virtual channelmatrix (E shown in the expression (17)) in consideration of the mapping.Then, replicas (ΞS′) of the received signals output from the channelmultiplier 144 are input to the canceller 114, and the aforementionedsubtraction expressed by the expression (2) is performed.

The base station device 510 of the second embodiment repeats a series ofoperations, such as the cancelling of replicas, the equalization, thespatial-and-spectral demapping, the decoding, and the generation ofreplicas, and thereby gradually increases the reliability of the decodedbits. After the series of operations is repeated the predeterminednumber of times, the determining units 131 and 132 perform harddetermination on bits, and thereby transmission data is reproduced.According to the configuration of the reception device, the signals onwhich multiple users perform spatial-and-spectral mapping can bedemultiplexed to decode respective transmission data pieces.

The base station device of the second embodiment includes theinterference power estimator 147 that measures the power of an unknowninterference signal received from another cell or the like for eachsubcarrier and for each transmission antenna. The measured power is usedfor calculation performed by the spectrum determining unit 146 using theexpression (1) (as Σm(k)). Additionally, the spectrum determining unit146 determines subcarriers to be used for transmission from each antennaof each mobile station device 500 or 501 based on the control flow ofthe first embodiment shown in FIG. 1. The spectrum determining unit 146outputs the mapping information indicative of the determined subcarriersto the transmitter 148. The transmitter 148 transmits the mappinginformation to the mobile station device 500 or 501 of the firstembodiment.

Regarding the above equalization, equalization with respect to the twopseudo transmission-data vectors shown in FIG. 7 is performed not onlyin the first operation but also in the second-or-later operation.Alternatively, the signal streams transmitted from the respectivetransmission antennas may be regarded as (pseudo) transmission-datavectors for equalization in the second-or-later operation. In this case,equalization with respect to four (pseudo) transmission-data vectors isperformed. Therefore, four DFT units, such as the elements 116 and 117,and four IDFT units, such as the elements 142 and 143, are required.Additionally, the virtual subchannel matrices (Ξ_(T1) and Ξ_(T2)) arerequired to be regenerated according to how transmission data vectorsare treated. Alternatively, equalization with respect to fourtransmission-data vectors may be performed in every operation from thefirst operation. In this case, the transmission-data vectors are signalstreams transmitted from the respective transmission antennas. Even inthis case, calculation using the expression (22) has to be performedfour times.

FIG. 9 is a schematic block diagram illustrating a configuration of abase station device 511 having a different configuration as that shownin FIG. 6. Like reference numerals denote like blocks in FIGS. 6 and 9.The base station device 511 shown in FIG. 9 has a configuration suchthat the DFT units 116 and 117 and the IDFT units 142 and 143 aredeleted from the configuration of the base station device 510 shown inFIG. 6. The difference is whether an input to the signalequalizing-and-demultiplexing unit 115 is a time-domain signal or afrequency-domain signal. Frequency-domain replicas or the like may beinput to perform the MMSE equalization as shown in FIG. 9.

A block that performs interleaving with respect to the encoded bits isnot included in the transmission device of the first embodiment. A blockthat performs deinterleaving with respect to the demodulated bits is notincluded in the reception device of the second embodiment. However, ifthese blocks are added, much better characteristics can be achieved.This is because a probability density function of each encoding bit atthe time of reception can be approximated by the Gaussian distribution,thereby increasing the reliability of turbo equalization that has beentheoretically analyzed under the assumption that the function isoriginally the Gaussian distribution.

Third Embodiment

The first and second embodiments have explained the case wherespatial-and-spectral mapping is performed under the condition that thereare always two signals to be multiplexed onto each subcarrier. Asexplained in those embodiments, if signals interfering with one anothercan be cancelled on the receiving side, spectral mapping may beindependently performed for each antenna on each transmitting side inconsideration of only a channel variation. The following embodimentexplains a mapping method of each transmission antenna independentlydetermining a spectrum to be used when the number of signals to bemultiplexed is not limited as in the first and second embodiments.

FIG. 10 illustrates a flow for determining subcarriers to be used forimplementing the third embodiment. Like reference numerals denote likeoperations in FIGS. 1 and 10. The difference from FIG. 1 is that theoperation in step S4 is deleted. This difference depends on the factthat the limit of the number of signals to be multiplexed onto onesubcarrier is deleted. By determining a spectrum to be used for eachtransmission antenna in this manner, a mapping achieving a more-flexibleand higher diversity effect can be achieved compared to the mapping ofthe first and second embodiments.

FIG. 11 illustrates a relationship between transmission antennas andspectra to be used when it is assumed for simplicity that the number ofsubcarriers to be used is 6, and mapping is performed for two users eachhaving two transmission antennas based on the control flow shown in FIG.10. FIG. 12 is a schematic block diagram illustrating a configuration ofa base station device 512 receiving a signal subjected to such aspatial-and-spectral mapping. Like reference numerals denote like blocksin FIGS. 9 and 12. When spatial-and-spectral mapping is performed usingthe control flow of the third embodiment shown in FIG. 10, transmissionfrom a maximum of four antennas is performed using the same spectrum.For this reason, the base station device 512 of the third embodimentincludes four reception systems (the antenna 100 to the DFT unit 110,the antenna 101 to the DFT unit 111, the antenna 310 to the DFT unit320, and the antenna 311 to the DFT unit 321) so as to demultiplex asignal generated by multiplexing a maximum of four signals. Compared tothe configuration shown in FIG. 9, channel estimators (channelestimators 322 and 323) are added, and there are four channelestimators.

An operation of each block of the base station device 512 is similar tothose of the base station devices 510 and 511. However, (pseudo)transmission-data vectors used for the signalequalizing-and-demultiplexing unit 300 equalizing signals subjected tothe spatial-and-spectral mapping of the third embodiment are signalstreams transmitted from the respective transmission antennas. As shownin FIG. 13, those signals are four signal streams expressed by shadedblocks B9, B10, and B11, white blocks B12, B13, and B14, blocks markedwith diagonal lines B15, B16, and B17, and hatched blocks B18, B19, andB20.

The signal equalizing-and-demultiplexing unit 300 performs an operationsimilar to equalization explained in the second embodiment on thesetransmission-data vectors. Regarding the repeated operations,equalization is performed using a result of the canceller 200subtracting, from all received signals, replicas of all the receivedsignals generated in consideration of mapping on the transmitting side,and received signal replicas of the respective transmission-data vectorsreconfigured from the replicas of the respective transmission-datavectors and channel variations (virtual subchannel matrices) to whichthe respective transmission-data vectors are subjected.

The equalized signals are output as signal streams transmitted from therespective transmission antennas. For this reason, those signals areregarded as ones having already been spatially demapped. Therefore, thespectrum demapping unit 301 performs spectrum demapping for each of thesignal streams (transmission-data vectors) based on mapping information.Additionally, when replicas of transmitted signals are generated fromLLRs of bits subjected to error correction coding, signals input to thespectral mapping unit 302 through the DFT units 213 to 216 are signalstreams (transmission-data vectors) transmitted from the respectivetransmission antennas. For this reason, the spectral mapping unit 302may perform only spectral mapping on the respective transmission-datavectors without considering spatial mapping.

According to the configuration of the base station device 512, each ofthe transmission-data vectors can be demultiplexed to decodecorresponding data even when a spectrum to be used is determinedindependently for each transmission antenna based on the control flow ofthe third embodiment.

Fourth Embodiment

The first to third embodiments have explained the case where the channelmatrix generated by the base station devices 510, 511, and 512 fromfrequency responses among transmission-and-reception antennas has noRank-deficiency, i.e., the case where the number of reception antennasis equal to or greater than that of transmission streams. However, afourth embodiment explains a demodulation method in a case ofRank-deficiency, i.e., a case where the number of reception antennas issmaller than that of transmission streams. It is assumed that the numberof transmission users, the number of transmission antennas of each user,and positions and the number of subcarriers to be used are the same asthose in the third embodiment. The number of reception antennas isassumed to be 2.

It is assumed that data is configured as packets each including multiplesymbols. Additionally, it is assumed that error correction coding isperformed in units of packets each corresponding to one user, and that 3data pieces are transmitted from each transmission-antenna, i.e., atotal of 6 data pieces are transmitted by one symbol. Further, it isassumed that 3 subcarriers are used for 1 symbol and for eachtransmission antenna.

FIG. 14 illustrates a relationship between transmission antennas andsubcarriers to be used at the time of transmission. S_(x-y)(p) denotesdata generated by a transmitted signal being converted into frequencysignals. A frequency vector S_(x-y) of transmitted signals is datagenerated by a time vector D_(x-y) of transmitted signals beingconverted into frequency vectors. x and y denote the user number and theantenna number, respectively. p denotes a natural number indicative ofan index of data. Frequency-domain transmitted signal vectors S1 and S2are defined as expressions (23) and (24) based on the allocation shownin FIG. 14.

$\begin{matrix}{{S\; 1} = \begin{bmatrix}{S_{1 - 1}\left( {{3\; p} - 2} \right)} \\0 \\{S_{1 - 1}\left( {{3\; p} - 1} \right)} \\0 \\0 \\{S_{1 - 1}\left( {3\; p} \right)} \\{S_{1 - 2}\left( {{3\; p} - 2} \right)} \\0 \\0 \\0 \\{S_{1 - 2}\left( {{3\; p} - 1} \right)} \\{S_{1 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (23) \\{{S\; 2} = \begin{bmatrix}0 \\{S_{2 - 1}\left( {{3\; p} - 2} \right)} \\{S_{2 - 1}\left( {{3\; p} - 1} \right)} \\0 \\0 \\{S_{2 - 1}\left( {3\; p} \right)} \\{S_{2 - 2}\left( {{3\; p} - 2} \right)} \\0 \\0 \\0 \\{S_{2 - 2}\left( {{3\; p} - 1} \right)} \\{S_{2 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (24)\end{matrix}$

The channel matrices Ξ1 and Ξ2 for each user are defined as expressions(25) and (26) where n denotes a transmission antenna (transmissionantennas 1 and 2 of the user 2 are assumed to be transmission antennas 3and 4 for convenience), j denotes a reception antenna, k denotes thesubcarrier number, Ξ_(jn)(k) denotes a frequency response for eachsubcarrier. In this case, frequency-domain data R received by a receivercan be shown in an expression (27).

$\begin{matrix}{{\Xi 1} = \begin{bmatrix}{\Xi_{\; 11}(1)} & \; & \; & \; & \; & \; & {\Xi_{\; 12}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{\; 11}(3)} & \; & \; & \; & \; & \; & 0 & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & 0 & \; & 0 & \; & \; & \; & {\Xi_{\; 12}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{\; 11}(6)} & \; & \; & \; & \; & \; & {\Xi_{\; 12}(6)} \\{\Xi_{\; 21}(1)} & \; & \; & \; & \; & \; & {\Xi_{\; 22}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & \; & 0 & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{\; 21}(3)} & \; & \; & \; & \; & \; & 0 & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & 0 & \; & 0 & \; & \; & \; & {\Xi_{\; 22}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{\; 21}(6)} & \; & \; & \; & \; & \; & {\Xi_{\; 22}(6)}\end{bmatrix}} & (25) \\{{\Xi 2} = \begin{bmatrix}0 & \; & \; & \; & \; & \; & {\Xi_{\; 14}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{\; 13}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{\; 13}(3)} & \; & \; & \; & \; & \; & 0 & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & 0 & \; & 0 & \; & \; & \; & {\Xi_{\; 14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{\; 13}(6)} & \; & \; & \; & \; & \; & {\Xi_{\; 14}(6)} \\0 & \; & \; & \; & \; & \; & {\Xi_{\; 24}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{\; 23}(2)} & \; & \; & \; & 0 & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{\; 23}(3)} & \; & \; & \; & \; & \; & 0 & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & 0 & \; & 0 & \; & \; & \; & {\Xi_{\; 24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{\; 23}(6)} & \; & \; & \; & \; & \; & {\Xi_{\; 24}(6)}\end{bmatrix}} & (26)\end{matrix}$

where 0 is set to frequency responses of subcarriers not used fortransmission.

$\begin{matrix}{R = {\begin{bmatrix}{R_{1}(1)} \\{R_{1}(2)} \\{R_{1}(3)} \\{R_{1}(4)} \\{R_{1}(5)} \\{R_{1}(6)} \\{R_{2}(1)} \\{R_{2}(2)} \\{R_{2}(3)} \\{R_{2}(4)} \\{R_{2}(5)} \\{R_{2}(6)}\end{bmatrix} = {{{\Xi 1}\; S\; 1} + {{\Xi 2}\; S\; 2}}}} & (27)\end{matrix}$

Regarding R_(j)(k), j denotes the reception antenna number, and kdenotes the subcarrier number. Expression concerning noise is omittedfor simplicity.

When a virtual channel matrix Ξ having the same order can be generatedby exchanging elements between the channel matrices Ξ1 and Ξ2, i.e.,when a matrix Ξ free of Rank deficiency can be generated, data can bedemodulated by the method of the second embodiment. However, when amatrix Ξ free of Rank deficiency cannot be generated by exchangingelements between the channel matrices Ξ1 and Ξ2 as in the fourthembodiment, data cannot be demodulated by the method of the secondembodiment. The reason that a matrix Ξ free of Rank deficiency cannot begenerated is that a larger number of streams than that of the receptionantennas is transmitted on each subcarrier. In other words, thesubcarriers 1 and 6 are the causes.

Hereinafter, an embodiment of a base station device 513 that candemodulate data transmitted under this condition is explained.

FIG. 15 is a schematic block diagram illustrating a configuration of thebase station device 513 according to the fourth embodiment. Only blocksthat are required for reception and are in the state after the basestation device 513 has firstly performed frequency conversion onreception data are shown for simplification of explanations. Likereference numerals in FIGS. 9 and 15 have the same function. Thedifference from FIG. 9 is that the signal equalizing-and-demultiplexingunit is changed to two signal equalizing-and-demultiplexing units.Additionally, the spatial-and-spectral demapping unit 118 has adifferent function, and therefore is shown in a spatial-and-spectraldemapping unit 500. It is assumed that MMSE equalization is performedfor equalization. Signals required for the MMSE equalization areresidual signals after subtracting replica signals from receivedsignals, a channel matrix Ξ among transmission-and-reception antennas, achannel matrix Ξ_(n) (subchannel matrix) from a desired antenna (antennafrom which data is to be calculated), and a replica signal S′(frequency-domain data) for reconfiguring a desired signal.

The reason that the base station device 513 includes the two signalequalizing-and-demultiplexing units 201-1 and 201-2 is that the channelmatrix has Rank-deficiency, thereby requiring multiple operations. Todistinguish between two operation systems, one operation system iscalled operation system 1 and the other operation system is calledoperation system 2.

Operations for received signals are basically similar to those shown inFIG. 9, but explanations thereof are given with explanations ofdifferent operations of the fourth embodiment. It is assumed thatfrequency responses among transmission-and-reception antennas havealready been calculated using some method.

Received signals are subjected to frequency conversion in units ofsymbols and then input to the canceller 114. These signals are expressedas an expression (27). Similar to the above embodiments, the basestation device 513 performs the repeated operations in units of packets(by which error correction cording is performed). Since a replica is notgenerated in the first operation, an output of the channel multiplier144 is 0. In the second-or-later operation, replicas of transmittedsignals calculated using LLRs of respective data pieces are generated,and therefore replica signals are subtracted from the received signals.When replicas of the transmitted signals are perfectly reproduced,signals after the subtraction include only noise.

The signal equalizing-and-demultiplexing units 201-1 and 201-2 group thereceived signals into two groups for two operation systems. In otherwords, regarding the signal equalizing-and-demultiplexing unit 201-1 ofthe operation system 1, only signals assigned a code K1 or K2 aretransmitted as shown in FIG. 16A. Regarding the signalequalizing-and-demultiplexing unit 201-2 of the operation system 2, onlysignals assigned a code K3 or K4 are transmitted as shown in FIG. 16B.Therefore, signals assigned no code shown in FIG. 16A or 16B areregarded as noise in each operation system.

When pseudo transmission-data vectors to be processed in each operationsystem are assumed to be Ss1 and Ss2, these vectors are expressed asexpressions (28) and (29). Virtual channel matrices Ξ_(s1) and Ξ_(s2)corresponding to the respective pseudo transmission-data vectors areexpressed as the following expressions (30) and (31).

$\begin{matrix}{{{Ss}\; 1} = \begin{bmatrix}{S_{1 - 1}\left( {{3\; p} - 2} \right)} \\{S_{2 - 1}\left( {{3\; p} - 2} \right)} \\{S_{1 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{1 - 2}\left( {{3\; p} - 1} \right)} \\{S_{1 - 1}\left( {3\; p} \right)} \\{S_{1 - 2}\left( {{3\; p} - 2} \right)} \\0 \\{S_{2 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{2 - 2}\left( {{3\; p} - 1} \right)} \\{S_{1 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (28) \\{{{Ss}\; 2} = \begin{bmatrix}{S_{1 - 2}\left( {{3\; p} - 2} \right)} \\{S_{2 - 1}\left( {{3\; p} - 2} \right)} \\{S_{1 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{1 - 2}\left( {{3\; p} - 1} \right)} \\{S_{2 - 1}\left( {3\; p} \right)} \\{S_{2 - 2}\left( {{3\; p} - 2} \right)} \\0 \\{S_{2 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{2 - 2}\left( {{3\; p} - 1} \right)} \\{S_{2 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (29) \\{\Xi_{S\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & \; & \; & \; & \; & \; & {\Xi_{12}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{13}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{11}(3)} & \; & \; & \; & \; & \; & {\Xi_{13}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{12}(5)} & \; & \; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{11}(6)} & \; & \; & \; & \; & \; & {\Xi_{12}(6)} \\{\Xi_{21}(1)} & \; & \; & \; & \; & \; & {\Xi_{22}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{23}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{21}(3)} & \; & \; & \; & \; & \; & {\Xi_{23}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; & \; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{21}(6)} & \; & \; & \; & \; & \; & {\Xi_{22}(6)}\end{bmatrix}} & (30) \\{\Xi_{S\; 2} = \begin{bmatrix}{\Xi_{12}(1)} & \; & \; & \; & \; & \; & {\Xi_{14}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{13}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{11}(3)} & \; & \; & \; & \; & \; & {\Xi_{13}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{12}(5)} & \; & \; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{13}(6)} & \; & \; & \; & \; & \; & {\Xi_{14}(6)} \\{\Xi_{22}(1)} & \; & \; & \; & \; & \; & {\Xi_{24}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{23}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{21}(3)} & \; & \; & \; & \; & \; & {\Xi_{23}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; & \; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{23}(6)} & \; & \; & \; & \; & \; & {\Xi_{24}(6)}\end{bmatrix}} & (31)\end{matrix}$

These virtual channel matrices are generated by the channelreconfiguring unit 145. These virtual channel matrices are input to thesignal equalizing-and-demultiplexing units 201-1 and 201-2, subjected toMMSE equalization in the respective systems, and then output.

Hereinafter, an operation of the channel reconfiguring unit 145 isexplained similarly to the second embodiment. Frequency responsematrices received from the respective channel estimators 112 and 113 canbe expressed as expressions (32) and (33) similarly to the secondembodiment. The difference from the second embodiment is the assumptionthat the number of subcarriers is 6. When two masking vectors MV aregenerated correspondingly to the pseudo transmission-data streams, whichare referred to as MV1 and MV2, these vectors can be expressed asexpressions (34) and (35).

$\begin{matrix}{\Xi_{r\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & {\Xi_{11}(2)} & {\Xi_{11}(3)} & {\Xi_{11}(4)} & {\Xi_{11}(5)} & {\Xi_{11}(6)} \\{\Xi_{12}(1)} & {\Xi_{12}(2)} & {\Xi_{12}(3)} & {\Xi_{12}(4)} & {\Xi_{12}(5)} & {\Xi_{12}(6)} \\{\Xi_{13}(1)} & {\Xi_{13}(2)} & {\Xi_{13}(3)} & {\Xi_{13}(4)} & {\Xi_{13}(5)} & {\Xi_{13}(6)} \\{\Xi_{14}(1)} & {\Xi_{14}(2)} & {\Xi_{14}(3)} & {\Xi_{14}(4)} & {\Xi_{14}(5)} & {\Xi_{14}(6)}\end{bmatrix}} & (32) \\{\Xi_{r\; 2} = \begin{bmatrix}{\Xi_{21}(1)} & {\Xi_{21}(2)} & {\Xi_{21}(3)} & {\Xi_{21}(4)} & {\Xi_{21}(5)} & {\Xi_{21}(6)} \\{\Xi_{22}(1)} & {\Xi_{22}(2)} & {\Xi_{22}(3)} & {\Xi_{22}(4)} & {\Xi_{22}(5)} & {\Xi_{22}(6)} \\{\Xi_{23}(1)} & {\Xi_{23}(2)} & {\Xi_{23}(3)} & {\Xi_{23}(4)} & {\Xi_{23}(5)} & {\Xi_{23}(6)} \\{\Xi_{24}(1)} & {\Xi_{24}(2)} & {\Xi_{24}(3)} & {\Xi_{24}(4)} & {\Xi_{24}(5)} & {\Xi_{24}(6)}\end{bmatrix}} & (33) \\{{{MV}\; 1} = \begin{bmatrix}1 & 0 & 1 & 0 & 0 & 1 \\1 & 0 & 0 & 0 & 1 & 1 \\0 & 1 & 1 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 1 & 0\end{bmatrix}} & (34) \\{{{MV}\; 2} = \begin{bmatrix}0 & 0 & 1 & 0 & 0 & 0 \\1 & 0 & 0 & 0 & 1 & 0 \\0 & 1 & 1 & 0 & 0 & 1 \\1 & 0 & 0 & 0 & 1 & 1\end{bmatrix}} & (35)\end{matrix}$

The same operation as performed in the second embodiment is performedbased on the vectors MV1 and MV2, and thereby the virtual channelmatrices Ξ_(s1) and Ξ_(s2) can be calculated as the expressions (30) and(31). Although elements of the fourth column disappear when zeroelements are deleted, 0 is inserted so as not to reduce the size of thematrix. Similarly, the virtual subchannel matrices (36) and (37) arecalculated based on the masking vector MV1.

Since the signal equalizing-and-demultiplexing units 201-1 and 201-2 ofthe fourth embodiment target the pseudo transmission-data vectors S_(s1)and S_(s2), Ξ_(nT) differs from information from an actual antenna.Operations are performed in the operation system 1 under the assumptionthat signals allocated to upper half elements of Ss1 are transmittedfrom the same antenna, and that signals allocated to lower half elementsof Ss1 are transmitted from the same antenna. Hereinafter, these pairsof signals are referred to as pseudo transmission-data vectors 1 and 2.Therefore, the signal equalizing-and-demultiplexing unit 201-1 performsequalization based on the channel matrix Ξ_(S1) shown in the expression(30), and the virtual subchannel matrices Ξ_(nT1) and Ξ_(nT2)corresponding to the pseudo transmission-data vectors 1 and 2. Thevirtual subchannel matrices Ξ_(nT1) and Ξ_(nT2) are expressed as thefollowing expressions.

$\begin{matrix}{\Xi_{{nT}\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & \; & \; & \; & 0 & \; \\\; & {\Xi_{13}(2)} & \; & \; & \; & \; \\\; & \; & {\Xi_{11}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{12}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{11}(6)} \\{\Xi_{21}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{23}(2)} & \; & \; & 0 & \; \\\; & \; & {\Xi_{21}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{21}(6)}\end{bmatrix}} & (36) \\{\Xi_{{nT}\; 2} = \begin{bmatrix}{\Xi_{12}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & {\; 0} & \; \\\; & \; & {\Xi_{13}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{12}(6)} \\{\Xi_{22}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{23}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{24}(6)}\end{bmatrix}} & (37)\end{matrix}$

At the same time, operations are performed in the operation system 2under the assumption that signals allocated to upper half elements ofSs2 are transmitted from the same antenna, and that signals allocated tolower half elements of Ss2 are transmitted from the same antenna.Hereinafter, these pairs of signals are referred to as pseudotransmission-data vectors 3 and 4.

Since the virtual subchannel matrix Ξ_(nT) is generated for each of thepseudo transmission-data vectors 1 to 4, four matrices are generated bythe channel reconfiguring unit 145.

The signal equalizing-and-demultiplexing units 201-1 and 201-2 use thereplica signals S′, which are generated based on the pseudotransmission-data vectors 1 to 4. The signalequalizing-and-demultiplexing unit 201-1 uses a replica of the pseudotransmission-data vector 1 and a replica of the pseudo transmission-datavector 2. The signal equalizing-and-demultiplexing unit 201-2 uses areplica of the pseudo transmission-data vector 3 and a replica of thepseudo transmission-data vector 4.

FIGS. 16A and 16B illustrate outputs after signal equalization anddemultiplexing, which are mapped onto a plane defined by actualuser-and-transmission-antennas and subcarriers. FIG. 16A illustratesoutputs of the signal equalizing-and-demultiplexing unit 201-1. FIG. 16Billustrates outputs of the signal equalizing-and-demultiplexing unit201-2. K1 and K2 denote signals to be processed as the pseudotransmission-data vectors 1 and 2, respectively. The hatched data denotedata to be simultaneously transmitted from the two systems.

The spatial-and-spectral demapping unit 500 maps the signals of K1 to K4onto inputs of the IDFT units 116, 117, 118, and 119 in a reversed orderof mapping performed at the time of transmission. At the time ofmapping, two data pieces output from the two operation systems(corresponding to hatched portions shown in FIGS. 16A and 16B) areaveraged. Alternatively, either one of the two outputs may beprioritized. The operation performed on data to be simultaneously outputfrom the two systems is the function that the spatial-and-spectraldemapping unit 204 does not have.

Additionally, another method may be considered in which frequencyelements causing a large interference effect are not used in the firstoperation. In other words, frequency elements of subcarriers, such assubcarrier 1 or 6, are not used.

FIG. 17 illustrates data input to the IDFT units 116 to 119 where x ofKx(y) denotes the virtual antenna number, and y of Kx(y) denotes thesubcarrier number at the time of outputting performed by the signalequalizing-and-demultiplexing unit 201-1 and 201-2. The input assigned Arequires addition, and the details of the addition are shown in FIG. 17.

The operation is performed by the spatial-and-spectral demapping unit500 in this manner, IDFT is performed for the respective signals, andthen LLRs for the respective data pieces are calculated by thedemodulators 122 and 123. The operations up to one performed by thedemodulators 122 and 123 are performed in units of symbols. The decoders124 and 125 generally perform error correction decoding in units bywhich encoding is performed. In this case, decoding is performed basedon the input LLRs. Then, LLR of respective data pieces are updated, andthe updated LLRs are input to the replica generators 209 and 210 exceptin the last repeated operation. In the last repeated operation, theupdated LLRs are output to the determining units 207 and 208.

The replicas generated by the replica generators 209 and 210 are inputto the DFT units 213, 214, 215, and 216 in units of symbols. s1-1(m)denotes a time domain replica with respect to data transmitted from theuser 1 antenna 1. s1-2(m) denotes a time domain replica with respect todata transmitted from the user 1 antenna 2. s2-1(m) denotes a timedomain replica with respect to data transmitted from the user 2antenna 1. s2-2(m) denotes a time domain replica with respect to datatransmitted from the user 2 antenna 2. m is an index of data. Threepieces of each replica are input to each of the DFT units 213 to 216.Outputs of the DFT units 213 to 216 are shown in FIG. 18. S′ denotes afrequency-domain replica. An index indicates the user number and theantenna number.

The spatial-and-spectral demapping unit 217 performs demapping on thefrequency-domain replicas according to the mapping used fortransmission. The data pieces subjected to demapping are expressed asexpressions (38) and (39) if expressed in the same format as theexpressions (23) and (24). The data pieces shown in the expressions (38)and (39) are multiplied by the channel information shown in theexpressions (25) and (26), and thereby a replica signal R′ to be usedfor cancelling is generated as shown in an expression (40).

$\begin{matrix}{{S^{\prime}1} = \begin{bmatrix}{S_{1 - 1}^{\prime}(1)} \\0 \\{S_{1 - 1}^{\prime}(2)} \\0 \\0 \\{S_{1 - 1}^{\prime}(3)} \\{S_{1 - 2}^{\prime}(1)} \\0 \\0 \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{1 - 2}^{\prime}(3)}\end{bmatrix}} & (38) \\{{S^{\prime}2} = \begin{bmatrix}0 \\{S_{2 - 1}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(2)} \\0 \\0 \\{S_{2 - 1}^{\prime}(3)} \\{S_{2 - 2}^{\prime}(1)} \\0 \\0 \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{2 - 2}^{\prime}(3)}\end{bmatrix}} & (39) \\{R^{\prime} = {\begin{bmatrix}{R_{1}^{\prime}(1)} \\{R_{1}^{\prime}(2)} \\{R_{1}^{\prime}(3)} \\{R_{1}^{\prime}(4)} \\{R_{1}^{\prime}(5)} \\{R_{1}^{\prime}(6)} \\{R_{2}^{\prime}(1)} \\{R_{2}^{\prime}(2)} \\{R_{2}^{\prime}(3)} \\{R_{2}^{\prime}(4)} \\{R_{2}^{\prime}(5)} \\{R_{2}^{\prime}(6)}\end{bmatrix} = {{{\Xi 1}\; S^{\prime}\; 1} + {{\Xi 2}\; S^{\prime}\; 2}}}} & (40)\end{matrix}$

The canceller 200 subtracts the replica signal R′ from the receivedsignal R. On the other hand, the spatial-and-spectral demapping unit 500has to generate a replica signal S_(S1)′ shown in an expression (41) anda replica signal S_(S2)′ shown in an expression (42) for each pseudotransmission-data vector required when the signalequalizing-and-demultiplexing unit 201-1 and 201-2 performsequalization.

$\begin{matrix}{{S^{\prime}s\; 1} = \begin{bmatrix}{S_{1 - 1}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(1)} \\{S_{1 - 1}^{\prime}(2)} \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{1 - 1}^{\prime}(3)} \\{S_{1 - 2}^{\prime}(1)} \\0 \\{S_{2 - 1}^{\prime}(2)} \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{1 - 2}^{\prime}(3)}\end{bmatrix}} & (41) \\{{S^{\prime}s\; 2} = \begin{bmatrix}{S_{1 - 2}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(1)} \\{S_{1 - 1}^{\prime}(2)} \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{2 - 1}^{\prime}(3)} \\{S_{2 - 2}^{\prime}(1)} \\0 \\{S_{2 - 1}^{\prime}(2)} \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{2 - 2}^{\prime}(3)}\end{bmatrix}} & (42)\end{matrix}$

The upper half elements of the replica signal S_(S1)′ and the lower halfelements of the replica signal S_(S1)′ correspond to the transmittedsignals from the pseudo transmission-data vectors 1 and 2, respectively.The upper half elements of the replica signal S_(S2)′ and the lower halfelements of the replica signal S_(S2)′ correspond to the transmittedsignals from the pseudo transmission-data vectors 3 and 4, respectively.These signals are multiplied by the virtual subchannel matrix Ξ_(nT) asshown in the expression (36), and thereby desired signals to be requiredfor equalization are reconfigured.

Since a part of signal elements have to be treated as noise in thefourth embodiment, the precision of calculating LLRs is considered to bedegraded. However, the LLR improvement effect by error correction isused, thereby enabling calculation of transmission data by the repeatedoperations. Additionally, subcarriers having the best quality amongtransmission devices and transmission antennas can be used, therebyachieving high communication quality if interference is cancelled.Further, the number of streams to be mapped onto one subcarrier is nottheoretically limited, thereby simplifying scheduling.

Fifth Embodiment

The fourth embodiment has explained the method of improvingLLR-improvement precision by dividing the operation system into twosystems and simultaneously performing the repeated operations. A fifthembodiment explains a method of sequentially performing the repeatedoperations. The fourth embodiment has explained the case where thesignal equalizing-and-demultiplexing unit 201-1 and 201-2 generate pairsof pseudo transmission-data vectors irrespective of user data. The fifthembodiment explains a case where a pair of pseudo transmission-datavectors is basically generated for each user and for each antenna. Asfor the method of sequentially performing repeated operations as will beexplained in the fifth embodiment, a pair of pseudo transmission-datavectors has to be set for each user. However, a pair of pseudotransmission-data vectors may be set for each user also in the fourthembodiment.

Preconditions of the fifth embodiment are the same as those of thefourth embodiment.

FIG. 19 is a schematic block diagram illustrating a configuration of abase station device 514 according to the fifth embodiment. Only blockswhich are required for reception and are in the state after the basestation device 514 firstly performs frequency conversion on receptiondata are shown for simplification of explanations. Blocks assigned likereference numerals have the same functions in FIGS. 15 and 19. Thedifference from FIG. 15 is that the spatial-and-spectral demapping unit500 has a different function, and therefore is referred to as aspatial-and-spectral demapping unit 501, and that thespatial-and-spectral mapping unit 217 has a different function, andtherefore is referred to as a spatial-and-spectral mapping unit 502.

The number of signal equalizing-and-demultiplexing units 201 changes toone because of the sequential operations. It is assumed that thefrequency-domain MMSE equalization is used for equalization. Signalsrequired for the equalization are residual signals after replica signalsare subtracted from received signals, a channel matrix Ξ amongtransmission-and-reception antennas, a channel matrix (subchannelmatrix) Ξ_(nT) from desired antennas (antennas from which data are to becalculated), and replica signals (frequency-domain data) S′ forreconfiguring desired signals. As will be explained later, signalequalization and demultiplexing are performed in units of users.Regarding the order of operations, however, the odd-numbered operationsof the repeated operations are performed by the user 1, and theeven-numbered operations of the repeated operations are performed by theuser 2. Preferably, signals having better conditions are preferentiallyprocessed.

Operations to be performed on received signals are similar to thoseshown in FIG. 15, but explanations thereof are simply explained togetherwith explanations of different operations of the fifth embodiment. It isassumed that frequency responses among transmission-and-receptionantennas have already been calculated using some method.

Received signals are subjected to frequency conversion in units ofsymbols and then are input to the canceller 200. These signals are shownin an expression (27). Similar to the aforementioned embodiments, thebase station device 514 performs the repeated operations in units ofpackets (by which error correction cording is performed). Since areplica is not generated in the first operation, an output of thechannel multiplier 220 is 0. In the second-or-later operation, replicasof transmitted signals calculated using LLRs of respective data piecesare generated, and therefore the canceller 200 subtracts replica signalsfrom the received signals. When transmitted signal replicas areperfectly reproduced, signals after the subtraction include only noise.

The signal equalizing-and-demultiplexing unit 201 groups the receivedsignals into two groups. In other words, the signalequalizing-and-demultiplexing unit 201-1 assumes that only informationmarked by horizontal lines shown in FIG. 20A (signals from the user 1)has been transmitted in the odd-numbered operations of the repeatedoperations. Additionally, the signal equalizing-and-demultiplexing unit201 assumes that information marked by vertical lines as shown in FIG.20B (signals from the user 2) has been transmitted in the even-numberedoperations of the repeated operations. Since the subcarrier 3 has enoughdegree of freedom (there is only one datum to be identified in eachoperation system) and there are interference signals (squares marked byhorizontal-and-vertical lines), the interference signals aredemultiplexed using unused degrees of freedom. Although a signal of thesubcarrier 2 of the user 2 is regarded as a noise in the case of FIG.20A, this signal can also be demultiplexed as an interference signal. Anactual operation image is shown in FIGS. 20C and 20D. The hatchedinformation is regarded as noise.

When pseudo transmission-data vectors targeted for the respectiverepeated operations are assumed to be Ssod (odd-numbered operations) andSsev (even-numbered operations), these vectors are expressed asexpressions (43) and (44), respectively. Virtual channel matricesΞ_(sod) and Ξ_(sev) corresponding to the respective pseudotransmission-data vectors Ssod and Ssev are expressed as the followingexpressions (45) and (46), respectively.

$\begin{matrix}{{Ssod} = \begin{bmatrix}{S_{1 - 1}\left( {{3\; p} - 2} \right)} \\0 \\{S_{1 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{2 - 2}\left( {{3\; p} - 1} \right)} \\{S_{1 - 1}\left( {3\; p} \right)} \\{S_{1 - 2}\left( {{3\; p} - 2} \right)} \\0 \\{S_{2 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{1 - 2}\left( {{3\; p} - 1} \right)} \\{S_{1 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (43) \\{{Ssev} = \begin{bmatrix}{S_{1 - 2}\left( {{3\; p} - 2} \right)} \\{S_{2 - 1}\left( {{3\; p} - 2} \right)} \\{S_{2 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{1 - 2}\left( {{3\; p} - 1} \right)} \\{S_{2 - 1}\left( {3\; p} \right)} \\{S_{2 - 2}\left( {{3\; p} - 2} \right)} \\0 \\{S_{1 - 1}\left( {{3\; p} - 1} \right)} \\0 \\{S_{2 - 2}\left( {{3\; p} - 1} \right)} \\{S_{2 - 2}\left( {3\; p} \right)}\end{bmatrix}} & (44) \\{{\Xi\;{sod}} = \begin{bmatrix}{\Xi_{11}(1)} & \; & \; & \; & \; & \; & {\Xi_{12}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{11}(3)} & \; & \; & \; & \; & \; & {\Xi_{13}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{1}(5)} & \; & \; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{11}(6)} & \; & \; & \; & \; & \; & {\Xi_{14}(6)} \\{\Xi_{21}(1)} & \; & \; & \; & \; & \; & {\Xi_{22}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{21}(3)} & \; & \; & \; & \; & \; & {\Xi_{23}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; & \; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{21}(6)} & \; & \; & \; & \; & \; & {\Xi_{24}(6)}\end{bmatrix}} & (45) \\{{\Xi\;{sev}} = \begin{bmatrix}{\Xi_{12}(1)} & \; & \; & \; & \; & \; & {\Xi_{14}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{13}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{13}(3)} & \; & \; & \; & \; & \; & {\Xi_{11}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{12}(5)} & \; & \; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{13}(6)} & \; & \; & \; & \; & \; & {\Xi_{14}(6)} \\{\Xi_{22}(1)} & \; & \; & \; & \; & \; & {\Xi_{24}(1)} & \; & \; & \; & \; & \; \\\; & {\Xi_{23}(2)} & \; & \; & 0 & \; & \; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{23}(3)} & \; & \; & \; & \; & \; & {\Xi_{12}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; & \; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; & \; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{23}(6)} & \; & \; & \; & \; & \; & {\Xi_{24}(6)}\end{bmatrix}} & (46)\end{matrix}$

These virtual channel matrices are generated by the channelreconfiguring unit 221. These virtual channel matrices are input to thesignal equalizing-and-demultiplexing units 201 according to the repeatednumber of times, subjected to MMSE equalization for each case, and thenoutput.

Hereinafter, an operation of the channel reconfiguring unit is explainedsimilarly to the fifth embodiment. Frequency response matrices receivedfrom the respective channel estimators can be expressed as expressions(47) and (48) similarly to the fifth embodiment. When two maskingvectors MV are generated correspondingly to the pseudo transmission-datastreams, which are referred to as MV3 and MV4, these can be expressed asexpressions (49) and (50).

$\begin{matrix}{\Xi_{r\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & {\Xi_{11}(2)} & {\Xi_{11}(3)} & {\Xi_{11}(4)} & {\Xi_{11}(5)} & {\Xi_{11}(6)} \\{\Xi_{12}(1)} & {\Xi_{12}(2)} & {\Xi_{12}(3)} & {\Xi_{12}(4)} & {\Xi_{12}(5)} & {\Xi_{12}(6)} \\{\Xi_{13}(1)} & {\Xi_{13}(2)} & {\Xi_{13}(3)} & {\Xi_{13}(4)} & {\Xi_{13}(5)} & {\Xi_{13}(6)} \\{\Xi_{14}(1)} & {\Xi_{14}(2)} & {\Xi_{14}(3)} & {\Xi_{14}(4)} & {\Xi_{14}(5)} & {\Xi_{14}(6)}\end{bmatrix}} & (47) \\{\Xi_{r\; 2} = \begin{bmatrix}{\Xi_{21}(1)} & {\Xi_{21}(2)} & {\Xi_{21}(3)} & {\Xi_{21}(4)} & {\Xi_{21}(5)} & {\Xi_{21}(6)} \\{\Xi_{22}(1)} & {\Xi_{22}(2)} & {\Xi_{22}(3)} & {\Xi_{22}(4)} & {\Xi_{22}(5)} & {\Xi_{22}(6)} \\{\Xi_{23}(1)} & {\Xi_{23}(2)} & {\Xi_{23}(3)} & {\Xi_{23}(4)} & {\Xi_{23}(5)} & {\Xi_{23}(6)} \\{\Xi_{24}(1)} & {\Xi_{24}(2)} & {\Xi_{24}(3)} & {\Xi_{24}(4)} & {\Xi_{24}(5)} & {\Xi_{24}(6)}\end{bmatrix}} & (48) \\{{{MV}\; 3} = \begin{bmatrix}1 & 0 & 1 & 0 & 0 & 1 \\1 & 0 & 0 & 0 & \underset{\_}{1} & 1 \\0 & 0 & 1 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & \underset{\_}{1} & 0\end{bmatrix}} & (49) \\{{{MV}\; 4} = \begin{bmatrix}0 & 0 & 1 & 0 & 0 & 0 \\1 & 0 & 0 & 0 & 1 & 0 \\0 & 1 & 1 & 0 & 0 & 1 \\1 & 0 & 0 & 0 & 1 & 1\end{bmatrix}} & (50)\end{matrix}$

The same operation as performed in the second embodiment is performedbased on the vectors MV3 and MV4, and thereby the virtual channelmatrices Ξ_(s1) and Ξ_(s2) can be calculated as the expressions (45) and(46). Although elements of the second and the fourth columns shown inthe expression (49) disappear when zero elements are deleted, 0 isinserted so as not to reduce the size of the matrix. With respect to theexpressions (13) and (14) shown in the fifth embodiment, expressions(51) and (52) can be obtained using the masking vector MV3, andexpressions (53) and (54) can be obtained using the masking vector MV4.

$\begin{matrix}{{D\; 0\;{U\left( {{\Xi_{r\; 1} \cdot {\,^{*}{MV}}}\; 3} \right)}} = \begin{bmatrix}{\Xi_{11}(1)} & 0 & {\Xi_{11}(3)} & 0 & {\Xi_{12}(5)} & {\Xi_{11}(6)} \\{\Xi_{12}(1)} & 0 & {\Xi_{13}(3)} & 0 & {\Xi_{14}(5)} & {\Xi_{12}(6)}\end{bmatrix}} & (51) \\{{D\; 0\;{U\left( {{\Xi_{r\; 1} \cdot {\,^{*}{MV}}}\; 3} \right)}} = \begin{bmatrix}{\Xi_{21}(1)} & 0 & {\Xi_{21}(3)} & 0 & {\Xi_{22}(5)} & {\Xi_{21}(6)} \\{\Xi_{22}(1)} & 0 & {\Xi_{23}(3)} & 0 & {\Xi_{24}(5)} & {\Xi_{22}(6)}\end{bmatrix}} & (52) \\{{D\; 0\;{U\left( {{\Xi_{r\; 1} \cdot {\,^{*}{MV}}}\; 4} \right)}} = \begin{bmatrix}{\Xi_{12}(1)} & {\Xi_{13}(3)} & {\Xi_{11}(3)} & 0 & {\Xi_{12}(5)} & {\Xi_{13}(6)} \\{\Xi_{14}(1)} & 0 & {\Xi_{13}(3)} & 0 & {\Xi_{14}(5)} & {\Xi_{14}(6)}\end{bmatrix}} & (53) \\{{D\; 0\;{U\left( {{\Xi_{r\; 1} \cdot {\,^{*}{MV}}}\; 4} \right)}} = \begin{bmatrix}{\Xi_{22}(1)} & {\Xi_{23}(3)} & {\Xi_{21}(3)} & 0 & {\Xi_{22}(5)} & {\Xi_{23}(6)} \\{\Xi_{24}(1)} & 0 & {\Xi_{23}(3)} & 0 & {\Xi_{24}(5)} & {\Xi_{24}(6)}\end{bmatrix}} & (54)\end{matrix}$

Regarding the expressions (51) and (52), the upper and lower elements ofthe fifth column have to be exchanged to prioritize the user group.Additionally, regarding the expressions (53) and (54), the upper andlower elements of the third column have to be exchanged to prioritizethe user group. Similarly, the virtual subchannel matrices (55) and (56)are calculated based on the masking vector MV3.

The signal equalizing-and-demultiplexing unit 201 of the fifthembodiment allocates the transmitted signal vectors so as to recognizethat data from the same user and the same antenna have preferably beentransmitted from the same antenna. However, signals transmitted fromdifferent antennas are partially mixed to enhance the precision ofdemultiplexing. Consequently, the transmission-data vectors are pseudovectors. Therefore, the virtual subchannel matrix Ξ_(nT) differs fromthe virtual subchannel matrix from an actual antenna.

It is assumed in the odd-numbered operations that signals allocated toupper half elements of Ssod have been transmitted from the same antenna,and that signals allocated to lower half elements of Ssod have beentransmitted from the same antenna. Hereinafter, these pairs of signalsare referred to as signals from the pseudo transmission-data vector 1and signals from the pseudo transmission-data vector 2. Therefore, thesignal equalizing-and-demultiplexing unit 201 performs equalizationbased on the virtual channel matrix shown in the expression (45) and thevirtual subchannel matrices Ξ_(nT1) and Ξ_(nT2) corresponding to thepseudo transmission-data vectors 1 and 2. The virtual subchannelmatrices Ξ_(nT1) and Ξ_(nT2) are expressed as the following expressions(55) and (56).

$\begin{matrix}{\Xi_{{nT}\; 1} = \begin{bmatrix}{\Xi_{11}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{11}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{14}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{11}(6)} \\{\Xi_{21}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{21}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{24}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{21}(6)}\end{bmatrix}} & (55) \\{\Xi_{{nT}\; 2} = \begin{bmatrix}{\Xi_{12}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{13}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{12}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{12}(6)} \\{\Xi_{22}(1)} & \; & \; & \; & \; & \; \\\; & 0 & \; & \; & 0 & \; \\\; & \; & {\Xi_{23}(3)} & \; & \; & \; \\\; & \; & \; & 0 & \; & \; \\\; & 0 & \; & \; & {\Xi_{22}(5)} & \; \\\; & \; & \; & \; & \; & {\Xi_{22}(6)}\end{bmatrix}} & (56)\end{matrix}$

It is assumed in the even-numbered operations that signals allocated toupper half elements of Ssev have been transmitted from the same antenna,and that signals allocated to lower half elements of Ssev have beentransmitted from the same antenna. Hereinafter, these pairs of signalsare referred to as the pseudo transmission-data vector 3 and the pseudotransmission-data vector 4.

Since the virtual subchannel matrix Ξ_(nT) is generated for each of thepseudo transmission-data vectors 1 to 4, four matrices are generated bythe channel reconfiguring unit 221.

The signal equalizing-and-demultiplexing unit 201 uses the replicasignals S′, which are generated based on the pseudo transmission-datavectors. In the odd-numbered operations, the signalequalizing-and-demultiplexing unit 201 uses a replica of the pseudotransmission-data vector 1 and a replica of the pseudo transmission-datavector 2. In the even-numbered operations, the signalequalizing-and-demultiplexing unit 201 uses a replica of the pseudotransmission-data vector 3 and a replica of the pseudo transmission-datavector 4.

FIGS. 21A and 21B illustrate outputs after signal equalization anddemultiplexing, which are mapped onto a plane defined by actualuser-and-transmission-antennas and subcarriers. FIG. 21A illustratesoutputs of the signal equalizing-and-demultiplexing unit 201 in theodd-numbered operations. FIG. 21B illustrates outputs of the signalequalizing-and-demultiplexing unit 201 in the even-numbered operations.K1 and K2 denote signals to be processed as the pseudo transmissionvectors 1 and 2, respectively. The hatched data are deleted.

The spatial-and-spectral demapping unit 500 maps the signals of K1 to K4onto inputs of the IDFT units 116 and 117 in a reversed order of mappingperformed at the time of transmission.

FIG. 22 illustrates data input to the IDFT units 116 and 117 where x ofKx(y) denotes the virtual antenna number, and y of Kx(y) denotes thesubcarrier number at the time of outputting performed by the signalequalization and demultiplexing.

The operation is performed by the spatial-and-spectral demapping unit501 in this manner, IDFT is performed, and then LLR for each data pieceis calculated by the demodulator 122. The operations up to the operationperformed by the demodulator 122 are performed in units of symbols. Thedecoder 124 performs error correction decoding in units by whichencoding is performed. In this case, decoding is performed based on theinput LLRs. Then, LLR for respective data pieces are updated, and theupdated LLRs are output from the repetition controller 205 to thereplica generator 210 except for the last repeated operation. In thelast repeated operation, the updated LLRs are output from the repetitioncontroller 205 to the determining unit 207.

The generated replicas are input to the DFT units 213 and 214 in unitsof symbols. s1-1(m) denotes a time domain replica with respect to datatransmitted from the user 1 antenna 1. s1-2(m) denotes a time domainreplica with respect to data transmitted from the user 1 antenna 2.s2-1(m) denotes a time domain replica with respect to data transmittedfrom the user 2 antenna 1. s2-2(m) denotes a time domain replica withrespect to data transmitted from the user 2 antenna 2. m is an index ofdata. Three pieces of each replica are input to each of the DFT units213 and 214. Outputs of the DFT units 213 and 214 are shown in FIG. 23.S′ denotes a frequency-domain replica. An index indicates the usernumber and the antenna number.

The spatial-and-spectral demapping unit 217 performs mapping on thefrequency-domain replicas according to the mapping used fortransmission. The mapped data pieces are expressed as an expression (57)in the case of odd-numbered operations and an expression (58) in thecase of even-numbered operation if expressed by a matrix indicated bythe user number and the antenna number in the vertical direction, andthe subcarrier number in the horizontal direction. The data pieces shownin the expressions (57) and (58) are multiplied by the channelinformation shown in the expressions (25) and (26), and thereby areplica signal R′(i) to be used for cancelling is generated, which isshown in an expression (59) where i denotes an index indicative of therepeated number of times.

$\begin{matrix}{\mspace{79mu}{{S^{\prime}1} = \begin{bmatrix}{S_{1 - 1}^{\prime}(1)} \\0 \\{S_{1 - 1}^{\prime}(2)} \\0 \\0 \\{S_{1 - 1}^{\prime}(3)} \\{S_{1 - 2}^{\prime}(1)} \\0 \\0 \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{1 - 2}^{\prime}(3)}\end{bmatrix}}} & (57) \\{\mspace{79mu}{{S^{\prime}2} = \begin{bmatrix}0 \\{S_{2 - 1}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(2)} \\0 \\0 \\{S_{2 - 1}^{\prime}(3)} \\{S_{2 - 2}^{\prime}(1)} \\0 \\0 \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{2 - 2}^{\prime}(3)}\end{bmatrix}}} & (58) \\{{R^{\prime}(i)} = {\begin{bmatrix}{R_{1}^{\prime}(1)} \\{R_{1}^{\prime}(2)} \\{R_{1}^{\prime}(3)} \\{R_{1}^{\prime}(4)} \\{R_{1}^{\prime}(5)} \\{R_{1}^{\prime}(6)} \\{R_{2}^{\prime}(1)} \\{R_{2}^{\prime}(2)} \\{R_{2}^{\prime}(3)} \\{R_{2}^{\prime}(4)} \\{R_{2}^{\prime}(5)} \\{R_{2}^{\prime}(6)}\end{bmatrix} = {{\left( {i\;{mod}\; 2} \right) \times \left( {{{\Xi 1}\; S^{\prime}1} + {\begin{bmatrix}1 \\1 \\1 \\1 \\1 \\1 \\0 \\0 \\0 \\0 \\0 \\0\end{bmatrix}^{T} \times {R^{\prime}\left( {i - 1} \right)}}} \right)} + {\left( {\left( {i + 1} \right){mod}\; 2} \right) \times \left( {{{\Xi 2}\; S^{\prime}2} + {\begin{bmatrix}0 \\0 \\0 \\0 \\0 \\0 \\1 \\1 \\1 \\1 \\1 \\1\end{bmatrix}^{T} \times {R^{\prime}\left( {i - 1} \right)}}} \right)}}}} & (59)\end{matrix}$

T denotes transpose of a matrix. (x mod 2) denotes a reminder when x isdivided by 2. Because of the sequential operations, a replica matrix inthe previous operation is stored, and a replica newly calculatedaccording to the repeated number of times has to be updated.

The canceller 200 subtracts the replica R′ from the received signal R.On the other hand, the spatial-and-spectral demapping unit 501 has togenerate a replica signal S′_(od) shown in an expression (60) and areplica signal S′_(ev), shown in an expression (61) for each requiredpseudo transmission-data vector when the signalequalizing-and-demultiplexing unit 201 performs equalization.

$\begin{matrix}{{S^{\prime}{od}} = \begin{bmatrix}{S_{1 - 1}^{\prime}(1)} \\0 \\{S_{1 - 1}^{\prime}(2)} \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{1 - 1}^{\prime}(3)} \\{S_{1 - 2}^{\prime}(1)} \\0 \\{S_{2 - 1}^{\prime}(2)} \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{1 - 2}^{\prime}(3)}\end{bmatrix}} & (60) \\{{S^{\prime}{ev}} = \begin{bmatrix}{S_{1 - 2}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(1)} \\{S_{2 - 1}^{\prime}(2)} \\0 \\{S_{1 - 2}^{\prime}(2)} \\{S_{2 - 1}^{\prime}(3)} \\{S_{2 - 2}^{\prime}(1)} \\0 \\{S_{1 - 1}^{\prime}(2)} \\0 \\{S_{2 - 2}^{\prime}(2)} \\{S_{2 - 2}^{\prime}(3)}\end{bmatrix}} & (61)\end{matrix}$

The upper half elements of the replica signal S′_(od) and the lower halfelements of the replica signal S′_(od) correspond to the transmittedsignals from the pseudo transmission-data vectors 1 and 2, respectively.The upper half elements of the replica signal S′, and the lower halfelements of the replica signal S′_(ev) correspond to the transmittedsignals from the pseudo transmission-data vectors 3 and 4, respectively.These signals are multiplied by the virtual subchannel matrix Ξ_(nT) asshown in the expression (46), and thereby desired signals required forequalization are reconfigured.

According to the configuration, the size of the circuit can be greatlyreduced although the repeated number of times is increased.

Sixth Embodiment

The aforementioned embodiments have explained the mobile station devicethat performs transmission by spreading signals to the frequency domainusing DFT and then reconverting the frequency-domain signals intotime-domain signals using IDFT, and the base station devicecorresponding to the mobile station device. However, the presentinvention is applicable to a system that performs frequency spreadingnot by DFT, but by multiplying transmitted signals by spreading codes.Particularly when orthogonal codes indicated by phase rotations areused, the same signals as in the case of performing spreading using DFTare generated, and therefore the PAPR characteristics can be reduced.The sixth embodiment explains a case where frequency spreading isperformed using phase-rotation orthogonal spreading codes.

FIG. 24 is a schematic block diagram illustrating a configuration of amobile station device 502 according to the sixth embodiment.

The mobile station device 502 shown in FIG. 24 has the sameconfiguration as that of the transmission device 500 shown in FIG. 3except that the DFT units 401 and 4-2 of the mobile station device 500of the first embodiment shown in FIG. 3 are replaced withspreading-and-multiplexing units 50-1 and 50-2. Thespreading-and-multiplexing units 50-1 and 50-2 perform spreading andmultiplexing as shown in FIG. 25. It is assumed here that the codelength is 64, 64 phase-rotation orthogonal spreading codes are used, andtherefore the number of subcarriers to be used by one user is 64.

C1 to C64 shown in FIG. 25 denote spreading codes. Each element (chip)of the spreading code is as shown. D1 and D2 denote signals that havebeen modulated and converted into parallel signals. Firstly, thespreading-and-multiplexing units 50-1 and 50-2 multiply the modulatedsignals D1 and D2 by codes C1 and C2. In this case, the modulated signalD1 or the like is copied for the code length (64 copies in this case),and then multiplied by respective chips of the spreading codes. Then,the results of the multiplication are added for each chip, and therebythe signals multiplied by the codes are outputs of thespreading-and-multiplexing units 50-1 and 50-2.

Thus, even when the phase-rotation orthogonal spreading codes are usedinstead of DFT, signals similar to ones in the case of DFT can begenerated, thereby enabling transmission of signals includingsignal-user MIMO signals and multi-user MIMO signals which are mixed.Accordingly, the configuration of the reception device explained abovecan be applied to the case where the transmission device includes thespreading-and-multiplexing units. Additionally, an inverse spreadingunit that multiplies received signals by complex conjugates of thephase-rotation orthogonal spreading codes used on the transmitting sidemay be included instead of the IDFT units after the spatial-and-spectraldemapping unit 118 shown in FIG. 6 or the spatial-and-spectral demappingunit shown in FIG. 9. Further, the DFT unit for generating replicas maybe replaced with the spreading-and-multiplexing unit explained above.

As explained above, the sixth embodiment has explained the case whereorthogonal codes indicated by phase rotations. However, the presentinvention is not limited thereto, and is applicable to a case wherefrequency spreading is performed using other spreading codes.

It is assumed as an example in the following embodiments that atransmission scheme is SC-ASA, the number of transmission devices is 2,and the number of subcarriers is 64. Additionally, it is assumed thatthe number of subcarriers to be used by each transmission device is 32which is half the total number of subcarriers, similarly to theconventional SC-ASA. In this case, N_(d)=64 and N_(u)=32 where N_(d)denotes the number of subcarriers to be used by each transmissionstation, and N_(u) denotes the number of subcarriers in an availableband. Hereinafter, explanations are given using N_(d) and N_(u).Further, since it is assumed that OFDM is used as a multicarrier scheme,SC-ASA is occasionally called DFT-S-OFDM in the description. Thefollowing embodiments target generally-called uplink communication froma mobile station to a base station if not particularly specified.However, the communication targeted by the present invention is notlimited thereto.

Seventh Embodiment

FIG. 26 is a schematic block diagram illustrating a configuration of aradio communication system according to a seventh embodiment. In theseventh embodiment, mobile station devices A80 a and A80 b transmit datausing SC-ASA, and a base station device A70 receives the data. In theseventh embodiment, the base station device A70 determines spectrumallocation information pieces with respect to the respective mobilestation devices A801 and A80 b. The base station device A70 transmitsthe spectrum allocation information pieces to the respective mobilestation devices A80 a and A80 b. In this case, any transmission methodmay be used. FIG. 27 illustrates an example of subcarrier mappingaccording to the seventh embodiment. FIG. 27A illustrates transmissionspectra onto which transmission data A transmitted from the mobilestation device A80 a are mapped and transmission spectra onto whichtransmission data B transmitted from the mobile station device A80 b aremapped. FIG. 27B illustrates reception spectra received by the basestation device A70. It is assumed here for simplification ofexplanations that there is no distortion due to radio channels.

In the case of SC-ASA, the transmission station performs subcarriermapping in consideration of states of subcarriers used by othertransmission stations so that the reception station can independentlydemultiplex and detect a signal transmitted from each transmissionstation. Under the assumption of SC-ASA that signals blocked on the timeaxis are periodical functions, the blocked signals are subjected to DFTto obtain amplitude and phase of each subcarrier, and then informationconcerning the obtained amplitude and phase are transmitted based on themulticarrier scheme. Accordingly, each subcarrier includes informationconcerning the entire transmission data on the time axis. Even if someof subcarriers to which transmission data from one transmission stationare allocated (2 of 6 subcarriers in the case of FIG. 27B) overlaps someof subcarriers to which transmission data from another transmissionstation are allocated as blackened subcarriers shown in FIG. 27B,information concerning the transmission data transmitted from eachtransmission station can be obtained based on other subcarriers which donot overlap. For this reason, if the information is used for detectingsignals from the multiple transmission stations, a signal from eachtransmission station can be demultiplexed and detected. This respect isexplained hereinafter.

FIG. 28 is a schematic block diagram illustrating a configuration of themobile station device A80 a according to the seventh embodiment.Although not shown, the mobile station device A80 b has the sameconfiguration as that of the mobile station device A80 a. The mobilestation device A80 a of the seventh embodiment includes an encoder A1,an interleaver A2, a modulator A3, an S/P (Serial/Parallel) converterA4, a DFT unit A5, a spectral mapping unit A6, an IDFT unit A7, a P/S(Parallel/Serial) converter A8, a pilot signal generator A9, a pilotmultiplexer A10, a CP inserter A11, a D/A (Digital/Analog) converterA12, a radio unit A13, an antenna A14, and a receiver A42.

The encoder A1 performs error correction coding on transmission data Ato generate encoded bits. The interleaver A2 interleaves the encodedbits to randomize the encoded bits so that a probability densityfunction of each encoded bit at the time of reception can beapproximated by the Gaussian distribution based on the central limittheorem, and thereby the reliability of turbo equalization technique,which has been theoretically analyzed under the assumption that theprobability density function is originally the Gaussian distribution,can be improved. Then, the modulator A3 modulates the interleavedencoded bits. Then, the S/P converter A4 converts the modulated encodedbits into N_(u) samples of parallel signals. Then, DFT unit A5 performsDFT with N_(u) points to convert the parallel signals into frequencysignals. In this case, the DFT unit A5 uses FFT (Fast Fourier Transform)as DFT.

Then, the spectral mapping unit A6 maps the N_(u) samples offrequency-domain signals onto N_(u) points included in an availabletransmission band of N_(d) points based on spectrum allocationinformation that receiver A42 has received from the base station deviceA70. Then, the IDFT unit A7 performs IDFT to convert thefrequency-domain signals of N_(d) points mapped onto the N_(u) pointsinto time-domain signals of N_(d) points. Then, the P/S converter A8converts the time-domain signals into a serial signal. On the otherhand, the pilot signal generator A9 generates a known pilot signal forchannel estimation. The pilot signal is multiplexed onto the serialsignal output from the P/S converter A8.

Then, the CP inserter A11 inserts a cyclic prefix for reducinginterference between DFT-S-OFDM symbols into the multiplexed signal,i.e., a rearward wave of the multiplexed signal is copied and pasted tothe forward thereof. The reason that the cyclic prefix is used is thatwaves to be subjected to DFT in the DFT section are required to have aperiod that is an integral multiple of one period of a periodicalfunction. For this reason, if delayed-wave elements are present inmultipath channels, the functional periodicity of the delayed-waveelements of the received signal collapses on the receiving side.Consequently, subcarriers cannot be independently processed. On theother hand, if a cyclic prefix corresponding to the maximum delay timeof the channel is preliminarily inserted on the transmitting side, thecyclic prefix is removed on the receiving side so that the functionalperiodicity with respect to the delayed elements can be maintained.Consequently, each subcarrier can be independently processed. In otherwords, even if each subcarrier is allocated to an arbitral frequency,the subcarrier can be reproduced on the receiving side. Then, D/Aconverter A12 converts the signal into which the cyclic prefix has beeninserted is converted into an analog signal. The radio unit A13upconverts the analog signal into a radio-frequency signal to betransmitted from the antenna A14.

FIG. 29 is a schematic block diagram illustrating a configuration of thebase station device A70 of the seventh embodiment. The base stationdevice A70 includes: a demapping unit A50 that returns the arrangementof subcarriers; and a signal detector A60 that demultiplexes and detectssignals transmitted from the respective mobile station devices.

The demapping unit A50 includes an antenna A15, an A/D converter A16, aCP remover A17, a pilot demultiplexer A18, channel estimators A19-1 andA19-2, a spectrum-allocation determining unit A20,channel-characteristic demapping units A21-1 and A21-2, channelcharacteristic selectors A22-1 and A22-2, an S/P converter A23, a DFTunit A24, a spectral demapping unit A25, a transmitter A38, and a radiounit A39.

The signal detector A60 includes signal cancellers A26-1 and A26-2,signal equalizers A27-1 and A27-2, demodulators A28-1 and A28-2,deinterleavers A29-1 and A29-2, decoders A30-1 and A30-2, repeatednumber controllers A31-1 and A31-2, interleavers A32-1 and A32-2,replica generators A33-1 and A33-2, S/P converters A34-1 and A34-2, DFTunits A35-1 and A35-2, interference spectrum selectors A36-1 and A36-2,and determining units A37-1 and A37-2. Regarding the demapping unit A50and the signal detector A60, reference symbols Ax-1 and Ax-2 (x is anumber) denote signal processors that process signals concerningtransmission data pieces A and B, respectively.

Firstly, the radio unit A39 downconverts a received signal received bythe antenna A15 into a baseband signal. Then, the A/D converter A16converts the baseband signal into a digital signal. Then, the CP removerA17 removes a cyclic prefix, i.e., extracts valid symbols having theperiodicity. The valid symbols indicate symbols included in a sectionfor one period. Then, the pilot demultiplexer A18 demultiplexes thedigital signal from which the cyclic prefix has been removed into a datasignal and pilot signals, and outputs the pilot signals required fordetecting the transmission data A and B transmitted from the mobilestation devices A80 a and A80 b to the channel estimators A19-1 andA19-2, respectively.

Meanwhile, the S/P converter A23 converts the data signal demultiplexedby the pilot demultiplexer A18 into parallel signals. Then, the DFT unit(time-frequency converter) A24 performs a Fourier transform that is atime-frequency conversion to convert the parallel signals intofrequency-domain signals. Then, based on the spectrum allocationinformation received from the spectrum-allocation determining unit A20,the spectral demapping unit A25 extracts subcarriers on which thespectral mapping unit A6 of each of the mobile station devices A80 a andA80 b has allocated signals, and returns the arrangement of theextracted subcarriers to the original arrangement before the mapping hasbeen performed by the spectral mapping unit A6. It is assumed here thatM₁ denotes a matrix including N_(u)×N_(d) elements including 0 and 1 forthe spectral mapping unit A6 of the mobile station device A80 a to mapthe frequency-domain signals output from the DFT unit A5 ontosubcarriers. In other words, if the matrix M₁ is multiplied by a vectorR₁′ indicative of outputs of the DFT unit A5, then a vector R₁, which isthe frequency-domain signals mapped onto subcarriers, is obtained. Asshown in an expression (62-1), the matrix M₁ is an N_(u)×N_(d) matrix inwhich the column number is the subcarrier number in the originalarrangement, the row number is the subcarrier number after the mapping,only elements corresponding to the interleaving are 1, and all otherelements are 0.

$\begin{matrix}{M_{1} = \begin{bmatrix}0 & 1 & \ldots & 0 \\0 & 0 & \ldots & 1 \\\vdots & \vdots & \ddots & \vdots \\1 & 0 & \ldots & 0\end{bmatrix}} & (62)\end{matrix}$

Accordingly, when M₂ denotes a matrix for the spectral mapping unit A6of the mobile station device A80 b to map the frequency-domain signalsonto subcarriers, M₂ is expressed similarly to the matrix M₁. Thespectral demapping unit A25 obtains the demapped signals received fromthe mobile station devices A80 a and A80 b as shown in expressions(63-1) and (63-2). As will be explained later, information concerningthe matrices M1 and M2 are transferred from the spectrum-allocationdetermining unit A20 to the spectral demapping unit A25.R ₁ ′=M ₁ ^(T) R  (63-1)R ₂ =M ₂ ^(T) R  (63-2)

In the expressions (63-1) and (63-2), R denotes an N_(d)×1 complexreceived signal vector including all signals from the mobile stationdevices A80 a and A80 b, which are output from the DFT unit A24. T inthe upper right denotes a transpose matrix. R₁′ and R₂′ denote complexreceived signal vectors including all the demapped signals from therespective mobile station devices A80 a and A80 b.

On the other hand, the channel estimators A19-1 and A19-2 estimatefrequency responses of channels from the respective mobile stationdevices A80 a and A80 b to the base station device A70 based on thepilot signals that are received from the respective mobile stationdevices A80 a and A80 b and demultilexed by the pilot demultiplexer A18.Thus, the diagonal matrices as shown in the expressions (64-1) and(64-2) are obtained with respect to the transmission data A and Btransmitted from the mobile station devices A80 a and A80 b,respectively.

$\begin{matrix}{H_{1} = {{{diag}\left\{ {{H_{1}(1)},\ldots\mspace{14mu},{H_{1}\left( N_{d} \right)}} \right\}} = \begin{bmatrix}{H_{1}(1)} & 0 & \ldots & 0 \\0 & {H_{1}(2)} & \ldots & 0 \\\vdots & \vdots & \ddots & \vdots \\0 & 0 & \ldots & {H_{1}\left( N_{d} \right)}\end{bmatrix}}} & \left( {64\text{-}1} \right) \\{H_{2} = {{{diag}\left\{ {{H_{2}(1)},\ldots\mspace{14mu},{H_{2}\left( N_{d} \right)}} \right\}} = \begin{bmatrix}{H_{2}(1)} & 0 & \ldots & 0 \\0 & {H_{2}(2)} & \ldots & 0 \\\vdots & \vdots & \ddots & \vdots \\0 & 0 & \ldots & {H_{2}\left( N_{d} \right)}\end{bmatrix}}} & \left( {64\text{-}2} \right)\end{matrix}$

In the expressions (64-1) and (64-2), H_(m)(k) denotes a complex gain ofa channel corresponding to the k-th subcarrier, which is included inchannels from the m-th mobile station device (1st one is the mobilestation device A80 a, and 2nd one is the mobile station device A80 b) tothe base station device A70.

Then, channel matrices H₁ and H₂ output from the channel estimatorsA19-1 and A19-2 are input to the spectrum-allocation determining unitA20. The spectrum-allocation determining unit A20 determines subcarriersto be used by the respective mobile station devices A80 a and A80 bbased on the channel matrices H₁ and H₂. Then, the spectrum-allocationdetermining unit A20 outputs the matrices M₁ and M₂ indicative ofspectrum allocation information that is the determination result to thetransmitter A38, the spectral demapping unit A25, thechannel-characteristic demapping units A21-1 and A21-2, the channelcharacteristic selectors A22-1 and A22-2, and the interference selectorsA36-1 and A36-2. Upon receiving the matrices M₁ and M₂ indicative ofspectrum allocation information, the transmitter A38 transmits thespectrum allocation information to the mobile station devices A80 a andA80 b through the radio unit A39 and the antenna A15.

In this case, only information required for each mobile station devicemay be transmitted, such that only information concerning the matrix M₁is transmitted to the mobile station device A80 a. Alternatively, allthe spectrum allocation information pieces may be transmitted. Then, thechannel-characteristic demapping units A21-1 and A21-2 extract frequencyresponses of channels required for detecting desired signals from thechannel matrices H₁ and H₂ with use of the matrices M₁ and M₂ includedin the spectrum allocation information, respectively. Then,channel-characteristic demapping units A21-1 and A21-2 returns thearrangement of subcarriers to that of the frequency-domain signalsbefore the spectral mapping has been performed by the mobile stationdevices A80 a and A80 b.H ₁ ′=M ₁ ^(T) H ₁  (65-1)H ₂ ′=M ₂ ^(T) H ₂  (65-2)

In the expressions (65-1) and (65-2), a matrix H₁′ denotes frequencyresponses of channels required for detecting desired signals for themobile station device A80 a which are arranged correspondingly to themapping performed by the spectral mapping unit A6. A matrix H₂′ denotesfrequency responses of channels required for detecting desired signalsfor the mobile station device A80 b which are subjected to the similaroperation. At the same time, the channel characteristic selectors A22-1and A22-2 extract channel responses corresponding to the subcarriernumbers causing interference with the signals received from therespective mobile station devices A80 a and A80 b, rearrange the channelresponses to cancel the interference, and thus obtain matrices H₁ ^(int)and H₂ ^(int). In this case, the matrices H₁ ^(int) and H₂ ^(int) thatare frequency characteristics of the extracted interference signals canbe obtained from expressions (66-1) and (66-2).H ₁ ^(int) =M ₁ ^(T) H ₂  (66-1)H ₂ ^(int) =M ₂ ^(T) H ₁  (66-2)

The H₁′ and H₂′ that are characteristics of the desired signals and thematrices H₁ ^(int) and H₂ ^(int) that are frequency characteristics ofthe interference signals, which are obtained in this manner, are inputto the signal cancellers A26-1 and A26-2 and the signal equalizers A27-1and A27-2. The channel characteristic selectors A22-1 and A22-2 may beprovided after the channel-characteristic demapping units A21-1 andA21-2.

The signal detector A60 includes signal cancellers A26-1 and A26-2,signal equalizers A27-1 and A27-2, demodulators A28-1 and A28-2,deinterleavers A29-1 and S29-2, decoders A30-1 and A30-2, repeatednumber controllers A31-1 and A31-2, interleavers A32-1 and A32-2,replica generators A33-1 and A33-2, S/P converters A34-1 and A34-2, DFTunits A35-1 and A35-2, interference spectrum selectors A36-1 and A36-2,and determining units A37-1 and A37-2. If the mobile station devices A80a and A80 b do not include the interleaver A2 shown in FIG. 28, the basestation device A70 does not need to include the deinterleaver A29 andthe interleaver A32. Therefore, the base station device A70 does notneed to include the interleaver A32 and the deinterleaver A29,correspondingly to the mobile station devices A80 a and A80 b.

Explanations of the signal detector A60 will be given assuming anoperation of detecting the transmission data A transmitted from themobile station device A80 a. For this reason, the block assigned thereference symbol Ax-1 (x denotes the block number) shown in FIG. 29 ismainly targeted for the operation. When signals transmitted from themobile station device A80 b are detected, the block assigned thereference symbol Ax-2 is targeted, and therefore explanations ofdetection of the transmission data B transmitted from the mobile stationdevice A80 b are omitted here.

Signals output from the spectral demapping unit 25 include subcarriersoverlapping, as interference, some subcarriers of signals transmittedfrom the mobile station device A80 b, and are input to the signalcanceller A26-1. The signal canceller A26-1 cancels frequency-domainsignal replicas of the desired signals and interference signal replicasfrom received signals, and then calculates residual-signal elements.When Q₁ denotes a residual that is a residual-signal element output fromthe signal canceller A26-1, the residual Q₁ can be obtained as shown inan expression (67).Q ₁ =R ₁ ′−H ₁ ′S _(1rep) −H ₁ ^(int) S _(2rep) ^(int)  (67)

In the expression (67), the first term denotes demapped receivedsignals. The second term denotes signal replicas generated based on thereliability of their own signals. The third term denotes interferencesignal replicas generated based on the reliability of other signals.S_(1rep) denotes an N_(u)×1 signal-replica vector of desired signalsexpressed by frequency-domain complex numbers. S_(2rep) ^(int) denotesan N_(u)×1 signal-replica vector expressed by frequency-domain complexnumbers (signal replicas will be explained later), which is generated bythe signal detector (replica generator A33-2) detecting signalstransmitted from the mobile station device A80 b, and then extractingsignals of interfering subcarriers. As will be explained later,operations of the signal canceller A26-1 to the interference spectrumselector A36-1 are repeatedly performed on the same received signal.However, a signal replica is not generated in the first operation (i.e.,S_(1rep)=0, S_(2rep) ^(int)=0). For this reason, the signal cancellerA26-1 does not perform the cancelling operation shown in the expression(67), and outputs the demapped received signal instead of the residualQ₁.

The residual Q₁ obtained as shown in the expression (67) is input to thesignal equalizer A27-1. The signal equalizer A27-1 performs equalizationon the input signals. As an equalizing method, MMSE (Minimum Mean SquareError) equalization is generally used in many cases. Although the caseof using the MMSE equalization will be explained, alternatively, ZF(Zero-Forcing) for multiplying an inverse matrix of a channel matrix,QRD (QR Decomposition), or SQRD (Sorted QRD) may be used. The signalequalizer A27-1 performs signal equalization using the residual Q1, thefrequency responses H₁ of channels for desired signals, and the signalreplica S_(1rep) generated by the replica generator A33-1, which will beexplained later, in order to reconfigure desired signals. Specifically,the signal equalizer A27-1 calculates the optimal weight based on theresidual Q1, the frequency responses H₁, and the signal replicaS_(1rep), and outputs the final equalized time-domain signal z₁multiplied by the optimal weight. The output signal z₁ is expressed asan expression (68). In other words, the expression (68) indicates thatthe signal equalizer A27-1 simultaneously performs equalization ondesired signals and conversion from frequency-domain signals intotime-domain signals.z ₁=(1+γδ)⁻¹ [γs _(1rep) +F ^(H) ΨQ ₁]  (68)

In the above expression, γ and δ denote real numbers used forcalculation using H1, powers of received signals, noise dispersion, andthe like. Similarly, Ψ denotes a complex square matrix having the sizeof the DFT-S-OFDM symbols used for calculation using H1, noisedispersion, and the like. s_(1rep) denotes time-domain replicas.S_(1rep) denotes frequency-domain replicas. Since a replica is not inputin the first operation of the repeated operations from the signalcanceller A26-1 to the interference spectrum selector A36-1, then Q₁=R₁′and S_(1rep)=0 in the expression (68), which is equal to the case of theconventional MMSE equalization without cancelling.

The reason that the signal canceller A26-1 cancels all the replicas ofinterference signals and desired signals is that the signal equalizerperforms an inverse matrix calculation, and therefore the inverse matrixcalculation has to be performed a number of times corresponding to thenumber of symbols included in a DFT-OFDM symbol if cancelling andequalization are repeated with only the desired signals remained. On theother hand, if the residual after cancelling all the replicas is input,the residual can be equally treated by the signal equalizer A27-1, andtherefore all weights can be calculated with one inverse calculation bythe signal equalizer A27-1. For this reason, the residual Q1 and thereplicas S_(1rep) of the desired signals are independently input andreconfigured to decrease the amount of the inverse calculation.

The equalized signal z₁ is demodulated by the demodulator A28-1, andLLRs (Log-Likelihood Ratio) that are real numbers indicative of thereliability of encoded bits divided in units of bits from the signal z₁.The obtained LLRs of the encoded bits are arranged by the interleaver A6of the mobile station device (mobile station device A80 a), andrearranged back to the original arrangement by the deinterleaver A29-1.Then, the decoder A30-1 performs error correction on the rearrangedLLRs, and outputs the LLRs of the encoded bits with higher reliabilityand decoded data A obtained by performing error correction on theencoded bits.

Then, the LLRs of the encoded bits and the decoded data A output fromthe decoder A30-1 are input to the repeated number controller A31-1. Therepeated number controller (repetition controller) A31-1, which countsthe repeated number of times, controls repetition based on whether ornot the repeated number of times is the predetermined number of times.If the repeated operation is not repeated, the decoded data A is outputto the determining unit A37-1. If the repeated operation is repeated,the LLRs of the encoded bits are output to the interleaver A32-1. TheLLRs of the encoded bits are arranged by the interleaver A32-1 similarlyto the arrangement performed by the interleaver A2 of the mobile stationdevice A80 a, and input to the replica generator A33-1.

The replica generator A33-1 generates the signal replica S_(1rep) inproportion to the reliability according to the LLRs of the encoded bits.For example, when QPSK (Quadrature Phase Shift Keying) is used as amodulation scheme, and LLRs of bits constituting a QPSK symbolcorresponding to the k-th index are real numbers λ₁(k) and λ₂(k), thesignal replica s_(1rep)(k) can be expressed as an expression (69).

$\begin{matrix}{{s_{1\;{rep}}(k)} = {{\frac{1}{\sqrt{2}}{\tanh\left( \frac{\lambda_{1}(k)}{2} \right)}} + {j\frac{1}{\sqrt{2}}{\tanh\left( \frac{\lambda_{2}(k)}{2} \right)}}}} & (69)\end{matrix}$

The signal replica s_(1rep)(k) generated by the generator A33-1 usingthe expression (69) is input to the signal equalizer A27-1 toreconfigure only desired signal elements using the expression (68) atthe time of equalization. At the same time, the signal replicas_(1rep)(k) is converted by the S/P converter A34-1 into parallelreplicas to be cancelled by the signal canceller A26-1, and thenconverted by the DFT unit A35-1 into frequency-domain signals. A signalvector indicative of the replicas concerted into the frequency-domainsignals is S_(1rep) shown in the expression (67). Then, regardingsubcarriers overlapping transmitted signals from the mobile stationdevice A80 b, transmitted signals from the mobile station device A80 ainterfere with the transmitted signals from the mobile station deviceA80 b. Therefore, the interference spectrum selector A36-1 selects theinterfering subcarriers.

For example, when the 3rd and 19th subcarriers of the 32 subcarriersinterfere with the transmitted signals from the mobile station deviceA80 b, only the 3rd and 19th subcarriers are extracted from the 32subcarriers, and the remaining subcarriers are changed to 0, therebygenerating the frequency-domain interference replica, which is theinterference replica S_(1rep) ^(int) shown in the expression (67). Theexpression (67) is used when signals from the mobile station device A80a are demodulated, and therefore signals from the mobile station deviceA80 b are regarded as interference. For this reason, the interferencereplica S_(2rep) ^(int) assigned a suffix 2rep is used.

In other words, 2rep shown in the expression (67) indicates that signalsfrom the mobile station device A80 b interfere with signals transmittedfrom the mobile station device A80 a.

Then, the signals output from the interference selectors are input tothe signal cancellers A26-1 and A26-2. Then, detection of signalstransmitted from the mobile station device A80 a performed by the signalcanceller A26-1 to the interference spectrum selector A36-1 anddetection of signals transmitted from the mobile station device A80 bperformed by the signal canceller A26-2 to the interference spectrumselector A36-2 are repeatedly performed in parallel. These repeatedoperations are performed the predetermined number of times controlled bythe repetition controllers A31-1 and A31-2. Then, the determining unitA37-1 obtains decoded data A corresponding to the transmission data A ofthe mobile station device A80 a. The determining unit A37-2 obtainsdecoded data B corresponding to the transmission data B of the mobilestation device A80 b.

Although it has been explained in the seventh embodiment that theoperation for the signals transmitted from the mobile station device A80a and the operation for the signals transmitted from the mobile stationdevice A80 b are performed in parallel, targets for these signaloperations may alternately be changed so as to serially detect thesignals, and thereby the blocks of the signal cancellers A26-1 and A26-2and the later blocks can be shared.

According to the seventh embodiment, even if at least some subcarriersof multiple data signals transmitted from multiple transmission devices(mobile station devices) to the same reception device (base stationdevice) using SC-ASA overlaps and thereby interfere with each other, thereception device detects each signal, generates replicas of transmittedsignals based on the reliability of the signals, and thereby interferingsubcarriers are transferred to each other. Accordingly, the interferingsignals, which are problematic when the signals transmitted from eachmobile station device are detected, can be regarded as known signals.Consequently, all the interference can be removed, and therefore thesignals can be demultiplexed and detected. Therefore, even ifoverlapping subcarriers having high reception quality and hightransmission efficiency are allocated to the multiple transmissiondevices, subcarriers having good transmission efficiency can beallocated to each transmission device,

Additionally, signal cancelling and equalization are performed usingreplicas of transmitted signals before the transmission device hasmapped frequency-domain signals onto subcarriers. Accordingly,calculation may be performed only for the subcarriers, the number ofwhich is smaller than the number of all subcarriers included in theentire transmission band of the transmission device, thereby enabling areduction in the amounts of calculation for the signal cancelling andequalization.

Further, as long as the interference spectrum selectors A36-1 and A36-2extract only the least subcarriers causing interference, the amount ofcalculation required for generating known interference signals can bereduced.

Eighth Embodiment

An eighth embodiment explains a radio communication system including abase station device A71 and the mobile station devices A80 a and A80 b,in which the base station device A71 repeatedly cancels interferencesignals in the time-domain to serially detect multiple desired signals.FIG. 30 is a schematic block diagram illustrating a configuration of thebase station device A71 according to the eighth embodiment.Configurations of the mobile station devices A80 a and A80 b of theeighth embodiment are the same as those of the seventh embodiment.Therefore, explanations and drawings thereof are omitted here.

As shown in FIG. 30, the base station device A71 includes a receptionantenna A100, an A/D converter A101, a CP remover A102, a pilotdemultiplexer A103, channel estimators A104-1 and A104-2,channel-characteristic demapping-and-selecting units A105-1 and A105-2,a user changing unit A106, an interference signal canceller A107, afirst S/P converter A108, a DFT unit A109, a spectral demapping unitA110, a desired-signal canceller A111, a signal equalizer A112, ademodulator A113, a deinterleaver A114, a decoder A115, arepeated-number controller A116, an interleaver A114, a replicagenerator A118, a second S/P converter A119, a second DFT unit A120, aninterference spectrum selector A121, a spectral mapping unit A122, anIDFT unit A123, a P/S converter A124, a determining unit A125, a radiounit A126, a spectrum-allocation determining unit A127, and atransmitter A128.

The channel-characteristic demapping-and-selecting unit A105 is the sameas one of the seventh embodiment shown in FIG. 28.

Operations of like blocks in the seventh and eighth embodiments arebasically the same, and therefore explanations thereof are omitted here.Hereinafter, the difference from the base station device A70 thatcancels interference signals received from other users in the frequencydomain as shown in FIG. 29. The concept of the repeated operations isbasically the same, but the interference signal canceller A107 performscancelling in the time domain. For this reason, the spectral mappingunit A122 maps the spectra selected by the interference spectrumselector A107 again. The IDFT unit A123 generates time-domain replicas.The interference signal canceller A107 for cancelling interferencesignals is provided before the DFT unit A109. The user change controllerA106 is provided to extract signals by alternately cancellinginterference signals. The interference signal canceller A107 receivesuser change information indicative of which user corresponds to thedesired signal, and performs canceling using interference replicas ofsignals other than the desired signals and the channel characteristicsof the signals. Additionally, the user change information is also inputfrom the user change controller A106 to the desired-signal cancellerA111 performing cancelling using the desired signals output from the DFTunit A120, to the signal equalizer A112 equalizing the desired signals,and to the determining unit A125 determining which user correspond todecoded data.

According to the eighth embodiment, substantially the same effect asthat in the case of cancelling in the frequency domain (seventhembodiment) can be achieved. Additionally, if blocks having referencenumerals larger than that of the S/P converter A108 are provided for twosystems, parallel operation can be performed. Therefore, according tothe present invention, cancelling in the time-or-frequency domain,serial detection by one system, and parallel detection by multiplesystems can freely combined.

Ninth Embodiment

The ninth embodiment explains a detection method using cancellingwithout repeated operations. A radio communication system according tothe ninth embodiment includes a base station device A72 that is areception device, and two mobile station devices A82 a and A82 b thatare transmission devices. FIG. 31 is a schematic block diagramillustrating configurations of the mobile station devices A82 a and A82b according to the ninth embodiment. In the ninth embodiment, the basestation device A72 does not perform interference cancelling on a signalto be firstly detected. For this reason, the mobile station device A82 aof the two mobile station devices A82 a and A82 b, which transmits thesignal to be firstly detected by the base station device A72, uses anencoding rate having strong resistance to interference and noise.

The mobile station device A82 a shown in FIG. 31 includes an encoderA200 a, an interleaver A201, a modulator A202, an S/P converter A203, aDFT unit A204, a spectral mapping unit A206, an IDFT unit A207, an P/Sconverter A208, a pilot generator A209, a pilot demultiplexer A210, a CPinserter A211, a D/A converter A212, a radio unit A213, an antenna A214,and a receiver A215. The reference numerals A200 a, A201, A202, A203,A204, A206, A207, A208, A209, A210, A211, A212, A213, A214, and A215shown in FIG. 31 correspond to the reference numerals A1, A2, A3, A4,A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, and A42, respectively.Therefore, explanations thereof are omitted here.

As shown in FIG. 31, the encoders A200 a and A200 b of the mobilestation devices A82 a and A82 b use the different encoding rates betweenthe two devices. When r₁ and r₂ denote encoding rates for transmissiondata pieces C and D, which are used by the encoders A200 a and A200 b ofthe mobile station devices A82 a and A82 b, respectively, it is assumedthat r₁<r₂. Since the encoding rate used for channel encoding withrespect to the transmission data C is small, the encoding rate has largeresistance to noise and interference. For this reason, if the basestation device A72 decodes the transmission data C first with thesignals of the transmission data D kept as interference signals, whendetecting the transmission data D, the base station device A72 generatesinterference replicas based on results of decoding the transmission dataC, cancel the generated interference replicas from received signals, andthereby can detect the transmission data D.

FIG. 32 is a schematic block diagram illustrating a configuration of thebase station device A72 according to the ninth embodiment. The basestation device A72 includes an antenna A240, a radio unit A241, an A/Dconverter A216, a CP remover A217, a pilot demultiplexer A218, channelestimators A219-1 and A219-2, a spectrum-allocation determining unitA220, channel-characteristic demapping units A221-1 and A221-2, achannel-characteristic selector A222-1, a first S/P converter A223, afirst DFT unit A224, a spectral demapping unit A225, a first signalequalizer A226, a first demodulator A227, a first deinterleaver A228, afirst decoder A229, an interleaver A230, a replica generator A231, asecond S/P converter A232, a second DFT unit A233, an interferencespectrum selector A234, an interference signal canceller A235, a secondsignal equalizer A236, a second demodulator A237, a second deinterleaverA238, a second decoder A239, and a transmitter A242. Although there aretwo circuits (A226 to A229, and A236 to A239) required for detectingeach transmission data, those two circuits may be changed to one circuitso as to serially detect each transmission data piece.

The antenna A240 to the spectral demapping unit A225 shown in FIG. 32are the same as those of the seventh and eighth embodiments, andtherefore explanations thereof are omitted here. It is assumed here thatthe encoding rate for transmission data C is smaller. In this case,received signals corresponding to the transmission data C have strongerresistance to interference and noise. For this reason, the transmissiondata C is decoded first, and signals corresponding to the transmissiondata C are cancelled as interference when the transmission data D isdetected. Accordingly, only the channel-characteristic selector A222-1that extracts elements interfering with the transmission data D isincluded, and a channel-characteristic selector that extracts elementsinterfering with the transmission data C is not included. This isbecause the signals corresponding to the transmission data D are unknowninterference signals when the transmission data C is detected, andtherefore cancelling is not required. The channel-characteristicselector that extracts elements interfering with the transmission data Dmay be provided after the channel estimator A219-2.

Hereinafter, detection of signals is explained. With respect tofrequency-domain received signals corresponding to respectivetransmission data pieces output from the spectral demapping unit A225, areceived signal of a subcarrier including the transmission data C isinput to the first signal equalizer A226 to detect the transmission dataC first. Then, operations up to one performed by the first decoder A229are performed similarly to the seventh and eighth embodiments to outputdetermination values or LLRs of respective bits. In this case, somesubcarriers of the received signals corresponding to the transmissiondata C interfere with signals corresponding to transmission data D, butare regarded as unknown interference to detect the transmission data C.

The determination value of each bit output from the decoder A229 isprocessed as decoded data C as it is. At the same time, the decoded datais interleaved by the interleaver A230 to generate interference replicasfor detecting transmission data D. Then, the interleaved data is inputto the replica generator A231, and thereby frequency-domain signalreplicas are generated through the S/P converter A232 and the second DFTunit A233. The frequency-domain signal replicas are converted by the S/Pconverter A232 into parallel replicas. Then, the DFT unit A233 performsDFT to convert the parallel replicas into frequency-domain signalreplicas.

The interference spectrum selector A234 multiplies the frequency-domainsignal replicas by a complex gain of a channel corresponding to thenumber of an interference subcarrier input from thechannel-characteristic selector A222-1 to generate interferencereplicas. The interference signal canceller A235 removes the generatedinterference replicas from received signals of subcarriers includingtransmission data D input from the spectral demapping unit A225 tocancel only interference elements. The received signals from whichinterference has been cancelled are equalized by the second signalequalizer A236 and converted by the second demodulator A237 intorespective encoded bits. Then, arrangement of the encoded bits isreturned by the second deinterleaver A238 to the original arrangement.Then, the rearranged encoded bits are subjected to the error correctiondecoding performed by the second decoder A239, and thereby decoded dataD can be obtained.

According to the ninth embodiment, the mobile station devices A82 a andA82 b on the transmitting side preliminarily process one group ofsignals so as to be easily decoded. Then, the base station device A72preferentially detects signals that are easier to be decoded. Thedetected signals are regarded as known interference when the other groupof signals is detected, and thereby both groups of signals can bedetected. Additionally, not all subcarriers are used for generatinginterference replicas, and only subcarriers causing the interference areextracted by the interference spectrum selector A234, thereby reducingthe amount of calculation required.

As operations to enable easy decoding on the receiving side, not onlythe encoding rate, but also a modulation scheme or transmission powermay be controlled on the transmitting side. Additionally, the basestation device A72 may determine the encoding rate, the modulationscheme, and the transmission power as well as the spectrum allocation,and transit these items to the mobile station devices A82 a and A82 b.Although it has been explained in the ninth embodiment that the twomobile station devices A82 a and A82 b have different configurations,one mobile station device may include multiple transmission antennas andperform the same operations.

Tenth Embodiment

The seventh to ninth embodiments have explained the transmission devicethat perform DFT to spread signals to the frequency domain, performsIDFT to convert the frequency-domain signals into time-domain signals,and transmits the time-domain signals, and the reception devicecorresponding to the transmission device. A tenth embodiment explains asystem performing not DFT, but frequency spreading by multiplyingtransmitted signals by spreading codes. When orthogonal codes indicatedby phase rotations are used as spreading codes, the same signals as inthe case of spreading by DFT are generated, thereby reducing PAPRcharacteristics and peak powers of transmitted signals. If the peakpower is so high as to exceed a performance limit of an amplifier whenamplifying transmitted signals to obtain transmission powers, waveformsare distorted. However, the peak power is reduced in this manner,thereby enabling a reduction in distortion of waveforms at the time ofamplification. The tenth embodiment explains a case where frequencyspreading is performed using phase-rotation orthogonal spreading codes.

FIG. 33 is a schematic block diagram illustrating a configuration of amobile station device A83 that is a transmission device according to thetenth embodiment. Except that the DFT unit A5 of the mobile stationdevice A80 of the seventh embodiment shown in FIG. 28 is replaced with aspreading-and-multiplexing unit A300, other elements (A1, A2, A3, A4,A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, and A42) of the mobilestation device A83 shown in FIG. 33 have the same configurations asthose of the mobile station device A80 a shown in FIG. 28. Thespreading-and-multiplexing unit A300 performs spreading and multiplexingas shown in FIG. 34. It is assumed here that the spreading code lengthis 64, and 64 phase-rotation orthogonal spreading codes are used.Accordingly, the number subcarriers used by one user (mobile stationdevice A83) is also 64.

C1 to C64 shown in FIG. 34 denote spreading codes. Each element (chip)of the spreading code is a value indicated by phase rotation, such ase^(jθ×0), e^(jθ×1), and e^(jθ×2). e denotes the Napier number that isthe base of natural logarithm. j denotes an imaginary unit. Modulationsignals D1, D2, . . . , D64 are outputs of the S/P converter A4, whichare modulated by the modulator A3, and then converted into parallelsignals. The spreading-and-multiplexing unit A300 multiplies themodulation signals D1, D2, . . . , and D64 by the spreading codes C1,C2, . . . , and C64. In this case, the modulation signals D1 to D64 arecopied for the code length (64 in this case) and multiplied by therespective chips of the spreading codes. Then, the results of thesemultiplications are added for the respective chips, and the resultantcodes are multiplied, the result of which becomes an output of thespreading-and-multiplexing unit A300.

Also when phase-rotation orthogonal spreading codes are used instead ofDFT, signals similar to ones in the case of DFT can be generated,thereby enabling transmission of the present invention with spectrumallocation in which some overlapping subcarriers are shared with anotheruser. Accordingly, the reception device may be the base station deviceA70 having the configuration shown in FIG. 29 even when the mobilestation device A83 includes the spreading-and-multiplexing unit A300.The DFT units A35-1 and A35-2 for generating replicas in the case ofFIG. 29 may be replaced with the aforementionedspreading-and-multiplexing unit A300.

As explained above, the tenth embodiment has explained the case whereorthogonal codes indicated by phase rotations are used for frequencyspreading. However, the present invention is not limited thereto, andother orthogonal codes may be used for frequency spreading.

Eleventh Embodiment

It has been explained in FIG. 27 that the reliability of each bit isextracted from subcarriers free of interference. Accordingly, up to howmany same-numbered subcarriers of subcarriers to which signals subjectedto frequency spreading are to be allocated multiple transmission devicescan select, i.e., a rate of overlapping subcarriers shared with multipleusers (mobile station devices) can be determined. This determination isperformed with use of received SNR (unknown interference power isassumed to be included in N) that is the ratio of desired signals and(unknown) interference signals to noise power by the spectrum-allocationdetermining unit A20 of the base station device A70 in the case of theseventh embodiment, by the spectrum-allocation determining unit A127 ofthe base station device A71 in the case of the eighth embodiment, or bythe spectrum-allocation determining unit A220 of the base station deviceA72 in the case of the ninth embodiment. The unknown interference powerindicates the power of interference which is caused by neighboring cellsor another system using the same frequency band, and which cannot becancelled.

Regarding an overlapping-subcarrier rate determining method usingreceived SNR according to the present embodiment, specifically, somethresholds regarding received SNR are preliminarily set, while thethresholds are correlated with the number of subcarriers allowed tooverlap. The greater the threshold is, a greater value is set to thenumber of overlapping subcarriers. Then, a received SNR of each user(average with respect to the band or some subcarriers) is measured.Then, it is determined in which range of one of the preliminarily setthresholds a result of the measurement is included, and thereby thenumber of overlapping subcarriers is calculated. In this case, if thereis a big difference in received SNR among multiple users, the smallestSNR may be compared to the threshold to determine the rate ofoverlapping subcarriers. Thus, the smallest received SNR among multipleusers is regarded as a reference, and thereby the reception device canproperly demodulate signals transmitted from each user while preventingthe number of overlapping subcarriers from increasing.

Apart from this, the rate of overlapping subcarriers can be determinedusing the input-output relationship of the mutual information amountsbetween the signal equalizers A27-1 and A27-2 of the seventh embodimentand the input-output relationship of the mutual information amountsbetween the decoders A30-1 and A30-2 of the seventh embodiment. Also inthe eighth embodiment, the rate can be similarly determined using thesignal equalizer A112 and the decoder A115. Hereinafter, as a method ofdetermining the rate of overlapping subcarriers using the input-outputrelationship of the mutual information amounts, a determining methodusing an EXIT (Extrinsic Information Transfer) chart for analyzinginternal repeated operations such as the turbo principle is explained.

FIG. 35 illustrates an example of the EXIT chart. The horizontal andvertical axes shown in FIG. 35 denote the input mutual informationamount of the signal equalizer and the output mutual information amountof the signal equalizer, respectively. Since the mutual informationamount output from the signal equalizer is input to the decoder in therepeated operations, the vertical axis indicates the input mutualinformation amount of the decoder. Since the output of the decoder isthe input mutual information amount of the signal equalizer, thehorizontal axis indicates the mutual information amount of the decoder.The mutual information amount is the maximum information amount that canbe obtained with respect to a signal X from a received signal Y when thesignal X is transmitted and then the received signal Y is obtained.Since the mutual information amount is the maximum value of theinformation amount with respect to X obtained from the log likelihoodrate Y in the case of analysis based on the EXIT chart, the maximumvalue is fixed to 1.

As shown in FIG. 35, a curve L301 denotes the input-output relationshipof the mutual information amount of the decoder where the horizontal andvertical axes denote an output and an input, respectively. Since thelarger power is required as the encoding rate increases, the curveshifts upward. On the other hand, a curve L302 denotes the input-outputrelationship of the mutual information amount of the signal equalizerwhere the horizontal and vertical axes denote an input and an output,respectively. Although the characteristics of the decoder (curve L301)are uniquely defined based on the encoding rate, the characteristics ofthe signal equalizer (curve L302) shift upward and downward, andtherefore the encoding rate of, for example, 1% is used.

A viewpoint of FIG. 35 is explained here. Explanations are given with anexample of a series of repeated operations from the operation of thesignal canceller A26-1 to the operation of the interference spectrumselector A36-1. Since the input mutual information amount of the signalequalizer A27-1 is 0 in the first operation, the mutual informationamount at the point A can be obtained as the output (this point iscalled a start point).

Then, since the output mutual information amount of the signal equalizerA27-1 is the input mutual information amount of the decoder A30-1, theoutput mutual information amount of the decoder A30-1 shifts asindicated by the doted line, and then shifts to a point B. After similaroperations are repeated, the mutual information amount shifts to pointsC, D, E, and F (F is called an end point), and thus the internal stateduring the repeated operations is illustrated. The end point when avalue on the horizontal axis is 1 indicates that all of otherinterference elements are cancelled, and the value is the rate of thereceived power of only the desired signals to noise power.

In other words, even if other signals are multiplexed at the time oftransmission, the other signals are cancelled by means of interferencereplicas. Accordingly, perfect demultiplexing can be performedirrespective of other signals. The dotted line indicating this movementis called an EXIT locus. In this case, it can be determined whether ornot transmission data can be detected by the repeated operations. If thecurve of the decoder does not cross the line of the signal equalizer andis under the line of the signal equalizer as shown in FIG. 35, the EXITlocus reaches the end point where the horizontal value is 1, which is adesirable state.

FIG. 36 illustrates the EXIT chart when the number of subcarriers to beused by multiple users varies. In FIG. 36, a curve L303 denotes thecharacteristic of the signal equalizer when no subcarrier overlaps. Acurve L304 denotes the characteristic of the signal equalizer when Ksubcarriers overlap. A curve L305 denotes the characteristic of thesignal equalizer when L subcarriers overlap. A curve L306 denotes thecharacteristic of the decoder. It is assumed here that L>K. Also in FIG.36, the mutual information amount finally obtained increases as themutual information amount input to the signal equalizer increases. Aswill be explained in a twelfth embodiment, this is because subcarriershaving good channel gains can be selected while the predetermined numberof subcarriers (K and L subcarriers in this case) is allowed to overlap.For this reason, each transmission terminal can perform transmissionusing subcarriers having better channel conditions, i.e., receivedpowers of desired signals finally obtained becomes large. On the otherhand, the mutual information amount to be obtained decreases as theinput mutual information amount decreases. This is because interferencecaused by overlapping subcarriers are not cancelled in the first stage,and therefore the interference have to be processed as unknowninterference, which corresponds to the first operation of the seventhembodiment shown in FIG. 35.

In the case of FIG. 36, lines for up to K overlapping subcarriers areabove the line L306 of the decoder, and therefore these overlappingsubcarriers can be demultiplexed by the repeated operations. On theother hand, the line L303 for the L overlapping subcarriers crosses thecurve L306 of the decoder. In this case, even if the EXIT locus isdrawn, the locus ends at the cross point, and therefore thecharacteristic cannot be improved. In other words, the interference istoo strong to be cancelled by extracting the reliability. Accordingly, athreshold allowing up to K subcarriers to overlap can be set in thiscase.

On the other hand, if L subcarriers are required to overlap, the curveL306 of the decoder is shifted downward. To implement this, the encodingrate may be reduced, and the resistance to the interference in the earlystage of the repeated operations may be enhanced.

Thus, when the encoding rate is fixed, the number of overlappingsubcarriers can be changed, and an EXIT locus is drawn, and thereby thenumber of overlapping subcarriers can be determined. On the other hand,when the number of overlapping subcarriers is limited, the encoding rateof the decoder is reduced so that a line of the decoder shifts downward.Therefore, the encoding rate or an encoding method (such as turbo codingor convolution coding) may be changed. Consequently, flexibility can beenhanced when the system design is optimized.

When the repeated operations are not performed as in the case of theninth embodiment, the operation ends at the point B shown in FIG. 35.For this reason, the precision of signals to be detected first isenhanced if a value of the point B on the horizontal axis (output mutualinformation amount of the decoder) is set closer to 1, thereby makingdetection of signals to be detected later easier.

Twelfth Embodiment

FIG. 37 is a flowchart illustrating a scheduling (subcarrier-allocationdetermining) method when a communication method in which some ofsubcarriers used by respective users overlap, i.e., the schedulingoperation of the spectrum-allocation determining unit A20 of the basestation device A70 in the case of the seventh embodiment, the schedulingoperation of the spectrum-allocation determining unit A127 of the basestation device A71 in the case of the eighth embodiment, and thescheduling operation of the spectrum-allocation determining unit A220 ofthe base station device A72 in the case of the ninth embodiment. In thepresent embodiment, FIG. 37 illustrates the case where the same numberof subcarriers is equally allocated to all users.

Regarding the scheduling method of the present embodiment shown in FIG.37, received SNR or SINR of each subcarrier is measured for each user(Sa1). Since an uplink scheduling method is targeted in the presentembodiment, the measurement in step S1 is performed by the base stationdevice. In step Sa2, all subcarriers are set as selectable subcarriersthat can be selected by all users (mobile station devices).Additionally, z(k)=0 for all subcarriers k (k denotes the subcarriernumber).

z(k) denotes a function indicative of the number of spectra (signals)overlapping each subcarrier. In step Sa3, y(x)=0 for all users x (xdenotes the user number). y(x) denotes a function indicative of thenumber of overlapping subcarriers shared by user x and another user. Inthe twelfth embodiment, scheduling is performed such that y(x) is equalto or less than the predetermined number of subcarriers (for example,the number set in the eleventh embodiment, which is denoted as A).

In the present embodiment, each user sequentially selects a subcarrierone by one. In the following operations, a subcarrier corresponding tothe user number “x” is selected. In step Sa4, however, x=1 for the firstoperation, and then a subcarrier corresponding to the user number “1” isselected. Then, a subcarrier having the highest received SNR or SINRamong selectable subcarriers corresponding to the user number “x” is setas a candidate subcarrier, as shown in step Sa5. When the number ofsubcarrier set as the candidate subcarrier is k, it is determined instep Sa6 whether or not the value of the function z(k) for the candidatesubcarrier k is 0.

If z(k)=0, i.e., if the candidate subcarrier k is not selected by anyuser, the routine proceeds to step Sa1 in which the candidate subcarrierk is allocated to the user corresponding to the user number “x”, and 1is added to z(k). If z(k)≠0, i.e., if the candidate subcarrier k isselected by another user, the routine proceeds to step Sa1 in which itis determined whether or not y(x) is smaller than the predeterminedsubcarrier number A. If y(x)≧A as a result of the determination in stepSa11, the user corresponding to the user number “x” cannot share theoverlapping subcarrier used by the other user any more, and thereforethe routine proceeds to step Sa12 in which the candidate subcarrier k isdeleted from the selectable subcarriers corresponding to the user number“x”. Then, the routine returns to step Sa5 in which a subcarrier havingthe highest received SNR or SINR among the selectable subcarriers otherthan the candidate subcarrier deleted in step Sa12 is set as a candidatesubcarrier for another allocation to be tried.

On the other hand, if y(x)<A as the result of the determination in stepSa11, the user corresponding to the user number “x” can share theoverlapping subcarrier used by the other user. Then, the routineproceeds to step Sa13 in which it is determined whether or not thenumber of users already allocated to the candidate subcarrier k (usershaving already selected the candidate subcarrier k) is 1. If the numberof users already allocated to the candidate subcarrier k is not 1 (i.e.,equal to or greater than 2), 1 is added to y(x) in step Sa16, thecandidate subcarrier k is allocated to the user corresponding to theuser number “x” in step Sa1, and then 1 is added to z(k).

If it is determined in step Sa13 that the number of users alreadyallocated to the candidate subcarrier k is 1, the routine proceeds tostep Sa14 in which it is determined whether or not y(x′) with respect tothe user x′ already allocated to the candidate subcarrier k is smallerthan the predetermined number of subcarriers A. If y(x′)≧A, the usercorresponding to the user number x′ cannot share the overlappingsubcarrier used by the other user any more, the user corresponding tothe user number x, who wants to share the candidate subcarrier k withthe other user corresponding to the user number x′, cannot select thecandidate subcarrier k. Therefore, the routine proceeds from step Sa14to step Sa12 in which the candidate subcarrier k is deleted from theselectable subcarriers with respect to the user number x, then returnsto step S5 in which another subcarrier allocation is tried.

If y(x′)<A in step Sa14, the user x′ can share an overlapping subcarrierwith other users (user x in this case). Therefore, 1 is added to y(x′)and y(x) in step Sa15 and Sa16, and then the routine proceeds to stepSa7 in which the candidate subcarrier k is allocated to the usercorresponding to the user number x.

After subcarriers are allocated in step Sa7, the candidate subcarrier kis deleted from the selectable subcarriers with respect to the user x instep Sa8. Then, the user number corresponding to a user currentlytargeted for allocation in step Sa9 is compared to the number of allusers to determine whether or not one cycle of allocation to every useris performed. If the user number corresponding to the user currentlytargeted for allocation in step Sa9 is not identical to the number ofall users, one cycle of allocation to every user has not yet beenperformed, and there are users who have not yet selected the same numberof subcarriers other users have already selected. Therefore, the usernumber is updated in step Sa17, and then the routine returns to stepSa5.

If the user number corresponding to the user currently targeted forallocation in step Sa9 is identical to the number of all users, itindicates that one cycle of allocation to every user has already beenperformed. Therefore, the routine proceeds to step Sa10 in which z(k)are added for all the subcarriers, and then divided by the number of allusers, and then it is determined whether or not the calculated number isidentical to the number of subcarriers to be allocated to each user. Ifthose numbers are identical to each other, it indicates that allsubcarriers to be allocated have already been allocated. Then, thescheduling of the twelfth embodiment ends. If those numbers are notidentical to each other, it indicates that all subcarriers to beallocated have not yet been allocated. Therefore, the routine returns tostep Sa4 in which allocation is sequentially performed from the user 1once again.

Conventionally, even if subcarriers having good received SNR or SINR areincluded in a transmittable band, and if the subcarriers are used byanother device, the subcarriers cannot be used. For this reason,scheduling for determining which subcarrier is to be allocated to whichtransmission device is determined based on the usage of the otherdevice, thereby making the scheduling algorithm complex.

According to the scheduling of the present embodiment, however,allocation can be performed in which the predetermined number ofsubcarriers or less can be shared with other users. Accordingly,scheduling can be performed without much consideration of the usage ofsubcarriers allocated to other users, thereby expanding a range ofselectable subcarriers, and therefore achieving communication usingsubcarriers having better channel conditions. Additionally, the numberof users to be simultaneously transmitted might be increased. For thisreason, this scheduling may be called flexible scheduling in whichlimited resources can be efficiently used.

Thirteenth Embodiment

FIGS. 38A and 38B illustrate examples of spectrum allocation whentransmission is performed using some overlapping subcarriers shared withmultiple users according to the present invention. FIG. 38A illustratesspectrum allocation when each of two users has selected ten subcarriersachieving good reception characteristics, which are included in a bandincluding 16 available subcarriers. It is assumed here that thepredetermined number of overlapping subcarriers that can be shared amongmultiple users is 4. When overlapping subcarriers can be shared amongusers, information corresponding to 20 subcarriers in total can betransmitted using 16 subcarriers as shown in FIG. 38A. When thepredetermined number of subcarriers is P, and the number of subcarriersavailable in the entire band is N_(d), it indicates that (N_(d)+P)/2subcarriers can be used by, for example, two users. Consequently, thepresent invention can be expected to greatly improve the transmissioncapacity.

Although FIG. 38A illustrates the case where subcarriers to be used bymultiple users with use of SC-ASA are mixed, and arbitral overlappingsubcarriers are shared with the users, alternatively, positions ofoverlapping subcarriers may be limited to some extent, not as in thecase of SC-ASA where each user can use arbitral subcarriers. Such a caseis shown in FIG. 38B. FIG. 38B illustrates a case where each of fourusers shares some overlapping subcarriers with other users. Allsubcarriers used by a user are continued. The overlapping subcarriersshared with the other users are edge subcarriers used by each user.Thus, users can be multiplexed by frequency division in which somesubcarriers are allowed to overlap. According to the configuration,transmission efficiency can be greatly improved compared to the systemin which frequencies are fully divided among users.

Fourteenth Embodiment

Generally, in a radio communication system, such as a cellular system,frames are formed by time-multiplexing multiple DFT-S-OFDM symbols(hereinafter called DFT-S-OFDM symbols) and then are transmitted. FIG.39 schematically illustrates the case of transmission per frame.Spectrum allocation per frame is also shown in FIG. 39. As shown in FIG.39, regarding scheduling of the present invention, selection ofsubcarriers may be changed in units of frames when each of thespectrum-allocation determining unit A20 of the base station device A70of the seventh embodiment, the spectrum-allocation determining unit A127of the base station device A71 of the eighth embodiment, or thespectrum-allocation determining unit A220 of the base station device A72of the ninth embodiment selects subcarriers in good conditions for eachuser, and transmission using overlapping subcarriers is performed.According to the configuration, interference from neighboring cellsvarying in units of frames is prevented in single-cell frequency reusesystem, thereby enabling higher transmission efficiency.

As shown in FIG. 39, selection of subcarriers is not required to bechanged in units of frames, and may be changed for each user only whenreceived SNR or SINR greatly varies. According to the configuration, theamount of control information required for communicating selectedsubcarriers can be reduced while subcarriers are selectedcorrespondingly to the channel conditions.

Although it has been explained in the seventh to fourteenth embodimentsthat the radio communication system includes two mobile station devicesthat are transmission devices, the number of mobile station devices maybe greater than 2. In this case, the maximum number of mobile stationdevices that can simultaneously allocate signals to one subcarrier istwo in the case of the above configuration of each base station device.However, for example, if the number of groups each including thereference numerals A19-1, A21-1, A22-1, A26-1, A27-1, A28-1, A29-1,A30-1, A31-1, A32-1, A33-1, A34-1, A35-1, A36-1, and A37-1 is increased,the maximum number of mobile station devices that can be simultaneouslyallocated can be increased up to the increased number of the groups.

It has been assumed in the seventh to fourteenth embodiments that eachradio communication system is one in which the mobile station device isthe transmission device, and the reception device is the base stationdevice. However, the radio communication system may be one usingwireless LAN in which the reception device is a base station, and atransmission device is a terminal including the spectrum-allocationdetermining unit.

Programs for implementing the functions of the encoder 1, the converter2, the S/P converter 3, the DFT units 4-1 and 4-2, the mapping units 5-1and 5-2, the IDFT units 6-1 and 6-2, the GI inserters 7-1 and 7-2, andthe P/S converters 8-1 and 8-2, which are shown in FIG. 3, may be storedin a computer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of the encoder 1, the modulator2, the S/P converter 3, the DFT unit 4-1, the mapping unit 5-3, the IDFTunits 6-1 and 6-2, the GI inserters 7-1 and 7-2, and the P/S converters8-1 and 8-2, which are shown in FIG. 5, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: CP removers 106 and 107; S/Pconverters 108, 109, 135, and 136; DFT units 110, 111, 116, 117, 137,138, 139, and 140; channel estimators 112 and 113; a canceller 114;signal equalizing-and-demultiplexing unit 115; a spatial-and-spectraldemapping unit 118; IDFT units 119, 120, 121, 122, 142, and 143; P/Sconverters 123 and 124; demodulators 125 and 126; decoders 127 and 128;repetition controllers 129 and 130; determining units 131 and 132;replica generators 133 and 134; a spatial-and-spectral mapping unit 141;a channel multiplier 144; a channel reconfiguring unit 145; a spectrumdetermining unit 146; an interference-power estimator 147; and atransmitter 148, which are shown in FIG. 6, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: CP removers 106 and 107; S/Pconverters 108, 109, 135, and 136; DFT units 110, 111, 116, 117, 137,138, 139, and 140; channel estimators 112 and 113; a canceller 114;signal equalizing-and-demultiplexing unit 115; a spatial-and-spectraldemapping unit 118; IDFT units 119, 120, 121, and 122; P/S converters123 and 124; demodulators 125 and 126; decoders 127 and 128; repetitioncontrollers 129 and 130; determining units 131 and 132; replicagenerators 133 and 134; a spatial-and-spectral mapping unit 141; achannel multiplier 144; a channel reconfiguring unit 145; a spectrumdetermining unit 146; an interference-power estimator 147; and atransmitter 148, which are shown in FIG. 9, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: CP removers 106, 107, 316,and 317; S/P converters 108, 109, 318, 319, 135, and 136; DFT units 110,111, 320, 321, 137, 138, 139, and 140; channel estimators 112, 113, 322,and 323; a canceller 114; signal equalizing-and-demultiplexing unit 300;a spatial-and-spectral demapping unit 301; IDFT units 119, 120, 121, and122; P/S converters 123 and 124; demodulators 125 and 126; decoders 127and 128; repetition controllers 129 and 130; determining units 131 and132; replica generators 133 and 134; a spatial-and-spectral mapping unit141; a channel multiplier 144; a channel reconfiguring unit 302; aspectrum determining unit 146; an interference-power estimator 147; anda transmitter 148, which are shown in FIG. 12, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: DFT units 110 and 111;channel estimators 112 and 113; IDFT units 119, 120, 121, and 122; P/Sconverters 123 and 124; demodulators 125 and 126; decoders 127 and 128;repetition controllers 129 and 130; determining units 131 and 132;replica generators 133 and 134; S/P converters 135 and 136; DFT units137, 138, 139, and 140; a spatial-and-spectral mapping unit 141; achannel multiplier 144; a channel reconfiguring unit 145; signalequalizing-and-demultiplexing units 201-1 and 201-2; and aspatial-and-spectral demapping unit 500, which are shown in FIG. 15, maybe stored in a computer-readable recording medium, and therebyoperations of the respective units may be performed by a computer systemreading the programs.

Programs for implementing the functions of: the DFT units 110 and 111;the channel estimators 112 and 113; the canceller 200; the signalequalizing-and-demultiplexing unit 201; the channel reconfiguring unit221; the channel multiplier 220; the spatial-and-spectral demapping unit501; the spatial-and-spectral mapping unit 502; the IDFT unit 115 and117; the P/S converter 120; the demodulator 122; the decoder 124; therepetition controller 205; the determining unit 207; the replicagenerator 210; the S/P converter 212; and the DFT units 215 and 216,which are shown in FIG. 19, may be stored in a computer-readablerecording medium, and thereby operations of the respective units may beperformed by a computer system reading the programs.

Programs for implementing the functions of the encoder 1, the modulator2, the S/P converter 3, the spreading-and-multiplexing units 50-1 and50-2, the mapping unit 5-1 and 5-2, the IDFT units 6-1 and 6-2, the GIinserters 7-1 and 7-2, the P/S converters 8-1 and 8-2, and the receiver11, which are shown in FIG. 24, may be stored in a computer-readablerecording medium, and thereby operations of the respective units may beperformed by a computer system reading the programs.

Programs for implementing the functions of: the encoder A1; theinterleaver A2; the modulator A3; the S/P converter A4; the DFT unit A5;the spectral mapping unit A6; the IDFT unit A7; the P/S converter A8;the pilot signal generator A9; the pilot multiplexer A10; and the CPinserter A11, which are shown in FIG. 28, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: the CP remover A17; thepilot demultiplexer A18; the channel estimator A19-1 and A19-2; thespectrum-allocation determining unit A20; the channel-characteristicdemapping units A21-2 and A21-2; the channel characteristic selectorsA22-1 and A22-2; the S/P converter A23; the DFT unit A24; the spectraldemapping unit A25; the signal cancellers A26-1 and A26-2; the signalequalizers A27-1 and A27-2; the demodulators A28-1 and A28-2; thedeinterleavers A29-1 and A29-2; the signal equalizers A27-1 and A27-2;the demodulators A28-1 and A28-2; the deinterleavers A29-1 and A29-2;the decoders A30-1 and A30-2; the repeated number controllers A31-1 andA31-2; the interleavers A32-1 and A32-2; the replica generators A33-1and A33-2; the S/P converters A34-1 and A34-2; the DFT units A35-1 andA35-2; and the interference spectrum selectors A36-1 and A36-2, whichare shown in FIG. 29, may be stored in a computer-readable recordingmedium, and thereby operations of the respective units may be performedby a computer system reading the programs.

Programs for implementing the functions of: the CP remover A102; thepilot demultiplexer A103; the channel estimators A104-1 and A104-2; thechannel-characteristic demapping-and-selecting units A105-1 and A105-2;the interference signal canceller A107; the S/P converter A108; the DFTunit A109; the spectral demapping unit A110; the desired signalcanceller A111; the signal equalizer A112; the demodulator A113; thedeinterleaver A114; the decoder A115; the repeated number controllerA116; the interleaver A117; the replica generator A118; the S/Pconverter A119; the DFT unit A120; the interference spectrum selectorA121; the spectral mapping unit A122; the IDFT unit A123; the P/Sconverter A124; the determining unit A125; and the spectrum-allocationdetermining unit A127, which are shown in FIG. 30, may be stored in acomputer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: the encoders A200 a and A200b; the interleaver A202; the modulator A202; the S/P converter A203; theDFT unit A205; the spectral mapping unit A206; the IDFT unit A207; theP/S converter A208; the pilot signal generator A209; the pilotmultiplexer A210; the CP inserter A211; and the D/A converter A212,which are shown in FIG. 31, may be stored in a computer-readablerecording medium, and thereby operations of the respective units may beperformed by a computer system reading the programs.

Programs for implementing the functions of: the CP remover A217; thepilot demultiplexer A218; the channel estimators A219-1 and A219-2; thespectrum-allocation determining unit A220; the channel-characteristicdemapping units A221-1 and A221-2; the channel-characteristic selectorA222-1; the S/P converter A223; the DFT unit A224; the spectraldemapping unit A225; the signal equalizer A226; the demodulator A227;the deinterleaver A228; the decoder A229; the interleaver A230; thereplica generator A231; the S/P converter A232; the DFT unit A233; theinterference spectrum selector A234; the interference signal cancellerA235; the signal equalizer A236; the demodulator A237; the deinterleaverA238; and the decoder A239, which are shown in FIG. 32, may be stored ina computer-readable recording medium, and thereby operations of therespective units may be performed by a computer system reading theprograms.

Programs for implementing the functions of: the encoder A1; theinterleaver A2; the modulator A3; the S/P converter A3; thespreading-and-multiplexing unit A300; the spectral mapping unit A6; theIDFT unit A7; the P/S converter A8; the pilot signal generator A9; thepilot multiplexer A10; and the CP inserter A11, which are shown in FIG.33, may be stored in a computer-readable recording medium, and therebyoperations of the respective units may be performed by a computer systemreading the programs.

The “computer system” described here includes OS and hardware, such asperipheral devices. The “computer-readable recording medium” includes aportable medium, such as flexible disk, an optical disc, an ROM, aCD-ROM, and the like, and a storage device such as a hard disk installedin a computer system. The “computer-readable recording medium” includesa medium dynamically storing a program for a short period, such as acommunication line when a program is transmitted through a network suchas the Internet or a communication line such as a telephone line.Additionally, the “computer-readable recording medium” includes a mediumstoring a program for a given period, such as volatile memory in acomputer system of a server or a client in the above case. The programmay be one for implementing a part of the aforementioned functions orone for implementing the aforementioned functions by combining anotherprogram stored in the computer system.

As explained above, embodiments of the present invention has beenexplained with reference to the drawings. The specific configuration isnot limited to these embodiments, and various modifications can be madewithout departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is suitable to, but not limited to, a mobilecommunication system performing uplink communication from a mobilestation device to a base station device using SC-ASA.

The invention claimed is:
 1. A communication device comprising: areceiver configured to receive first receiving signals and secondreceiving signals, wherein the first receiving signals are allocated toa first set of subcarriers composed of two or more continuoussubcarriers, the second receiving signals are allocated to a second setof subcarriers composed of two or more continuous subcarriers, and atleast a portion of the second set of subcarriers overlaps a portion ofthe first set of subcarriers in a time frame; and a demodulatorconfigured to detect the second receiving signals transmitted using oneor more subcarriers from receiving signals including the first receivingsignals and the second receiving signals, wherein the one or moresubcarriers are subcarriers such that the first set of subcarriersoverlap the second set of subcarriers, and the demodulator beingconfigured to demodulate the first receiving signals, wherein the firstreceiving signals are different signals from the second receivingsignals.
 2. The communication device according to claim 1, wherein thereceiver comprises one or more antennas, wherein the number of the oneor more antennas is less than the number of the receiving signals in thetime frame.
 3. The communication device according to claim 1, whereinthe demodulator is configured to demodulate information using repeatedoperations.
 4. The communication device according to claim 1, whereinthe number of the one or more subcarriers as the overlapping subcarriersis set for each time frame.
 5. A communication method for acommunication device, the communication method comprising: receivingfirst receiving signals and second receiving signals, wherein the firstreceiving signals are allocated to a first set of subcarriers composedof two or more continuous subcarriers, the second receiving signals areallocated to a second set of subcarriers composed of two or morecontinuous subcarriers, and at least a portion of the second set ofsubcarriers overlaps a portion of the first set of subcarriers in a timeframe; detecting the second receiving signals transmitted using one ormore subcarriers from receiving signals including the first receivingsignals and the second receiving signals, wherein the one or moresubcarriers are subcarriers such that the first set of subcarriersoverlap the second set of subcarriers, and the demodulator beingconfigured to demodulate the first receiving signals; and demodulatingthe first receiving signals; wherein the first receiving signals aredifferent signals from the second receiving signals.
 6. A base stationdevice comprising: a receiver configured to receive first receivingsignals transmitted by a first communication device and second receivingsignals transmitted by a second communication device, wherein the firstreceiving signals are allocated to a first set of subcarriers composedof two or more continuous subcarriers, the second receiving signals areallocated to a second set of subcarriers composed of two or morecontinuous subcarriers, and at least a portion of the second set ofsubcarriers overlaps a portion of the first set of subcarriers in a timeframe; and a demodulator configured to detect the second receivingsignals transmitted using one or more subcarriers from receiving signalsincluding the first receiving signals and the second receiving signals,wherein the one or more subcarriers are subcarriers such that the firstset of subcarriers overlap the second set of subcarriers, and thedemodulator being configured to demodulate information indicating bitsincluded in the first receiving signals, wherein the first receivingsignals are different signals from the second receiving signals.